U.S. patent application number 17/151077 was filed with the patent office on 2021-12-09 for syringe with two-stage sealing pressure.
The applicant listed for this patent is AbbVie Inc.. Invention is credited to Martin J. Gibler, Dennis Y. Lee, Sean E. Mackey, Ji Zhou.
Application Number | 20210379290 17/151077 |
Document ID | / |
Family ID | 1000005798814 |
Filed Date | 2021-12-09 |
United States Patent
Application |
20210379290 |
Kind Code |
A1 |
Mackey; Sean E. ; et
al. |
December 9, 2021 |
SYRINGE WITH TWO-STAGE SEALING PRESSURE
Abstract
A syringe includes a barrel, a plunger, and a sealing member
creating a seal between the plunger and the barrel. The barrel
includes a first portion with a first inner diameter and a second
portion with a second inner diameter that is larger than the first
inner diameter. The sealing member engages the first portion of the
barrel to give rise to a first contact pressure when the barrel is
filled with product. The first contact pressure is sufficient to
maintain a gas-tight seal over the expected temperature ranges
-25.degree. C. to 40.degree. C. A first force is applied to the
plunger to overcome the first contact pressure and move the plunger
out of the first portion and into the second portion to dispense
product. The sealing member engages the second portion of the
barrel to give rise to a second contact pressure that is lower than
the first contact pressure. A second force lower than the first
force is sufficient to overcome the second contact pressure and
move the plunger in the second portion to continue dispensing
product. The syringe may include a restraining element for
accommodating expansion of the product during freezing.
Inventors: |
Mackey; Sean E.; (Grayslake,
IL) ; Zhou; Ji; (Grayslake, IL) ; Gibler;
Martin J.; (West Chester, OH) ; Lee; Dennis Y.;
(Scotch Plains, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AbbVie Inc. |
North Chicago |
IL |
US |
|
|
Family ID: |
1000005798814 |
Appl. No.: |
17/151077 |
Filed: |
January 15, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15462131 |
Mar 17, 2017 |
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17151077 |
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13829251 |
Mar 14, 2013 |
9669165 |
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15462131 |
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61763777 |
Feb 12, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61M 5/31505 20130101;
A61J 15/0069 20130101; A61M 2005/3106 20130101; A61M 5/31513
20130101; A61J 15/0076 20150501; A61M 2005/3131 20130101; A61J
15/0015 20130101; A61M 5/14546 20130101; A61M 5/31501 20130101;
A61M 2005/31506 20130101; A61J 7/0053 20130101; A61M 5/3135
20130101; A61J 15/0061 20130101; A61M 2005/3101 20130101; A61M
2205/8206 20130101; A61M 5/002 20130101 |
International
Class: |
A61M 5/315 20060101
A61M005/315; A61M 5/145 20060101 A61M005/145 |
Claims
1. A syringe for use in a drug infusion system, the syringe
comprising: a barrel having a cylindrical wall, the cylindrical
wall having a first portion with a first inner diameter and a
second portion with a second inner diameter that is larger than the
first inner diameter; a plunger within the barrel; wherein a
sealing member of the plunger engages the first portion of the
barrel with a first contact pressure when the barrel is filled with
product, such that a first force is required to move the plunger
with respect to the barrel; wherein a portion of the plunger
engages the second portion of the barrel with a second contact
pressure that is lower than the first contact pressure, such that a
second force is required to move the plunger in the second portion;
and wherein the second force is lower than the first force.
2. The syringe of claim 1, wherein the first contact pressure gives
rise to a seal between the plunger and the first portion of the
barrel, which seal is gas-tight through a temperature range of
-25.degree. C. to 40.degree. C.
3. The syringe of claim 1, wherein the plunger includes at least
one o-ring; and wherein the o-ring gas-tightly seals against the
cylindrical wall of the barrel in both of the first and second
portions.
4. The syringe of claim 1, wherein the sealing member gas-tightly
seals against the first portion of the barrel; and does not
gas-tightly seal against the second portion of the barrel.
5. The syringe of claim 1, wherein the plunger includes a plunger
head with at least one rim in addition to the sealing member;
wherein the sealing member does not engage the second portion of
the barrel; and wherein the at least one rim engages the inner
surface of the second portion of the barrel.
6. The syringe of claim 1, wherein the first portion of the barrel
includes a reduced diameter member inserted into the barrel.
7. The syringe of claim 1, wherein the sealing member of the
plunger includes a flexible wiper.
8. The syringe of claim 1, wherein a step is defined between the
first and second portions of the barrel; and wherein the sealing
member engages the step to resist movement of the plunger in a
rearward direction with respect to the barrel.
9. A method for storing and dispensing a product having a high
content of water, the method comprising: providing a syringe barrel
having a cylindrical wall, the cylindrical wall having a first
portion with a first inner diameter and a second portion with a
second inner diameter that is larger than the first inner diameter;
providing a plunger having a sealing member; inserting the plunger
into the barrel; filling the syringe with product such that the
plunger is positioned within the first portion of the barrel;
engaging the first portion of the barrel with the sealing member to
give rise to a first contact pressure when the barrel is filled
with product; applying a first force to overcome the first contact
pressure and move the plunger out of the first portion and into the
second portion to dispense product; engaging the second portion of
the barrel with a portion of the plunger to give rise to a second
contact pressure that is lower than the first contact pressure; and
applying a second force lower than the first force to overcome the
second contact pressure move the plunger in the second portion to
continue dispensing product.
10. The method of claim 9, wherein giving rise to the first contact
pressure includes creating a gas-tight seal between the plunger and
barrel through a temperature range of -25.degree. C. to 40.degree.
C.
11. The syringe of claim 9, wherein providing a plunger having a
sealing member includes providing a plunger with at least one
o-ring as the sealing member; wherein engaging the second portion
of the barrel with a portion of the plunger includes engaging the
second portion of the barrel with the at least one o-ring; and
wherein the o-ring gas-tightly seals against both of the first and
second portions.
12. The syringe of claim 9, wherein engaging the first portion of
the barrel with the sealing member includes gas-tightly sealing the
plunger with respect to the first portion of the barrel with the
sealing member; and wherein engaging the second portion of the
barrel with a portion of the plunger does not include gas-tightly
sealing the plunger with respect to the second portion of the
barrel with the sealing member.
13. The syringe of claim 9, wherein providing a plunger having a
sealing member includes providing a plunger head having a sealing
member and at least one rim; and wherein engaging the second
portion of the barrel with a portion of the plunger includes
engaging the second portion of the barrel the at least one rim and
not with the sealing member.
14. The syringe of claim 9, further comprising inserting a reduced
diameter member into the barrel to create the first portion of the
barrel.
15. The syringe of claim 9, wherein providing a plunger having a
sealing member includes providing the plunger having a flexible
wiper as the sealing member.
16. The syringe of claim 9, further comprising defining a step
between the first and second portions of the barrel; and engaging
the step with the sealing member to resist movement of the plunger
in a rearward direction with respect to the barrel.
17. A method for storing and dispensing a product having water
content, the method comprising: providing a syringe barrel having a
front end, a rear end, and a cylindrical wall having an inner
surface, the rear end being open, and the front end including an
orifice; providing a plunger adapted to fit within the syringe
barrel with a sliding seal against the inner surface, a product
chamber being defined between the inner surface of the barrel and
the plunger; filling the product chamber with the product having
water content; attaching a restraining element to the syringe;
freezing the product-filled syringe such that the water content of
the product freezes and expands; restraining displacement of the
plunger with the restraining member during expansion of the water
content during freezing; storing the frozen product-filled syringe
until an approximate time of use; and at the approximate time of
use, thawing the frozen product-filled syringe and actuating the
plunger to dispense the thawed product from the syringe through the
orifice.
18. The method of claim 17, wherein restraining displacement of the
plunger includes abutting the restraining element with the plunger;
the method further comprising: pressing the plunger against the
restraining element with a force in response to expansion of the
water content during freezing.
19. The method of claim 18, further comprising accommodating
expansion of the water content during freezing by deflecting the
restraining element when the force exceeds a restraining element
deflection threshold.
20. The method of claim 18, further comprising accommodating
expansion of the water content during freezing by deflecting the
plunger when the force exceeds a plunger deflecting threshold.
21. The method of claim 17, wherein attaching a restraining element
includes affixing an end cap to the syringe.
22. The method of claim 17, wherein providing a syringe barrel
includes forming a mounting structure at the rear end, the mounting
structure adapted for mounting the syringe to a pump; and wherein
attaching the restraining element includes attaching the
restraining element to the mounting structure.
23. The method of claim 17, wherein attaching a restraining element
includes inserting the syringe into a case and affixing a cap to
the case; and wherein restraining displacement of the plunger
includes abutting the plunger against the cap.
24. The method of claim 17, wherein restraining displacement of the
plunger includes accommodating expansion of the freezing water
content with deflection of at least one of the plunger and
restraining element.
25. The method of claim 17, further comprising permitting
displacement of the plunger toward the restraining element during
freezing of the product-filled syringe, prior to restraining
displacement of the plunger with the restraining element.
Description
[0001] This application claims priority to U.S. Provisional
Application No. 61/763,777 filed Feb. 12, 2013, the entire contents
of which being incorporated by reference herein.
BACKGROUND
[0002] The present invention relates to a syringe for use in a drug
infusion system. The syringe is configured to have a relatively
tight seal when full, and a relatively loose seal as product is
being dispensed. The relatively tight seal helps maintain a
gas-tight seal between plunger and barrel during a freeze and thaw
cycle to which the syringe and product is exposed. The relatively
loose seal permits the plunger to be pushed down the barrel to
dispense product with lower force on the plunger, to reduce power
consumption of the pump and extend battery life.
SUMMARY
[0003] The invention provides a syringe for use in a drug infusion
system, the syringe comprising: a barrel having a cylindrical wall,
the cylindrical wall having a first portion with a first inner
diameter and a second portion with a second inner diameter that is
larger than the first inner diameter; a plunger within the barrel;
wherein a sealing member of the plunger engages the first portion
of the barrel with a first contact pressure when the barrel is
filled with product, such that a first force is required to move
the plunger with respect to the barrel; wherein a portion of the
plunger engages the second portion of the barrel with a second
contact pressure that is lower than the first contact pressure,
such that a second force is required to move the plunger in the
second portion; and wherein the second force is lower than the
first force.
[0004] In some embodiments, the first contact pressure gives rise
to a seal between the plunger and the first portion of the barrel,
which seal is gas-tight through a temperature range of -25.degree.
C. to 40.degree. C. In some embodiments, the plunger includes at
least one o-ring; and wherein the o-ring gas-tightly seals against
the cylindrical wall of the barrel in both of the first and second
portions. In some embodiments, the sealing member gas-tightly seals
against the first portion of the barrel; and does not gas-tightly
seal against the second portion of the barrel. In some embodiments,
the plunger includes a plunger head with at least one rim in
addition to the sealing member; wherein the sealing member does not
engage the second portion of the barrel; and wherein the at least
one rim engages the inner surface of the second portion of the
barrel. In some embodiments, the first portion of the barrel
includes a reduced diameter member inserted into the barrel. In
some embodiments, the sealing member of the plunger includes a
flexible wiper. In some embodiments, a step is defined between the
first and second portions of the barrel; and wherein the sealing
member engages the step to resist movement of the plunger in a
rearward direction with respect to the barrel.
[0005] The invention also provides a method for storing and
dispensing a product having a high content of water, the method
comprising: providing a syringe barrel having a cylindrical wall,
the cylindrical wall having a first portion with a first inner
diameter and a second portion with a second inner diameter that is
larger than the first inner diameter; providing a plunger having a
sealing member; inserting the plunger into the barrel; filling the
syringe with product such that the plunger is positioned within the
first portion of the barrel; engaging the first portion of the
barrel with the sealing member to give rise to a first contact
pressure when the barrel is filled with product; applying a first
force to overcome the first contact pressure and move the plunger
out of the first portion and into the second portion to dispense
product; engaging the second portion of the barrel with a portion
of the plunger to give rise to a second contact pressure that is
lower than the first contact pressure; and applying a second force
lower than the first force to overcome the second contact pressure
move the plunger in the second portion to continue dispensing
product.
[0006] In some embodiments, giving rise to the first contact
pressure includes creating a gas-tight seal between the plunger and
barrel through a temperature range of -25.degree. C. to 40.degree.
C. In some embodiments, providing a plunger having a sealing member
includes providing a plunger with at least one o-ring as the
sealing member; wherein engaging the second portion of the barrel
with a portion of the plunger includes engaging the second portion
of the barrel with the at least one o-ring; and wherein the o-ring
gas-tightly seals against both of the first and second portions. In
some embodiments, engaging the first portion of the barrel with the
sealing member includes gas-tightly sealing the plunger with
respect to the first portion of the barrel with the sealing member;
and wherein engaging the second portion of the barrel with a
portion of the plunger does not include gas-tightly sealing the
plunger with respect to the second portion of the barrel with the
sealing member. In some embodiments, providing a plunger having a
sealing member includes providing a plunger head having a sealing
member and at least one rim; and wherein engaging the second
portion of the barrel with a portion of the plunger includes
engaging the second portion of the barrel the at least one rim and
not with the sealing member. In some embodiments, the method
further comprises inserting a reduced diameter member into the
barrel to create the first portion of the barrel. In some
embodiments, providing a plunger having a sealing member includes
providing the plunger having a flexible wiper as the sealing
member. In some embodiments, the method further comprises defining
a step between the first and second portions of the barrel; and
engaging the step with the sealing member to resist movement of the
plunger in a rearward direction with respect to the barrel.
[0007] The invention also provides method for storing and
dispensing a product having water content, the method comprising:
providing a syringe barrel having a front end, a rear end, and a
cylindrical wall having an inner surface, the rear end being open,
and the front end including an orifice; providing a plunger adapted
to fit within the syringe barrel with a sliding seal against the
inner surface, a product chamber being defined between the inner
surface of the barrel and the plunger; filling the product chamber
with the product having water content; attaching a restraining
element to the syringe; freezing the product-filled syringe such
that the water content of the product freezes and expands;
restraining displacement of the plunger with the restraining member
during expansion of the water content during freezing; storing the
frozen product-filled syringe until an approximate time of use; and
at the approximate time of use, thawing the frozen product-filled
syringe and actuating the plunger to dispense the thawed product
from the syringe through the orifice.
[0008] In some embodiments, restraining displacement of the plunger
includes abutting the restraining element with the plunger; the
method further comprising: pressing the plunger against the
restraining element with a force in response to expansion of the
water content during freezing. In some embodiments, the method
further comprises accommodating expansion of the water content
during freezing by deflecting the restraining element when the
force exceeds a restraining element deflection threshold. In some
embodiments, the method further comprises accommodating expansion
of the water content during freezing by deflecting the plunger when
the force exceeds a plunger deflecting threshold. In some
embodiments, attaching a restraining element includes affixing an
end cap to the syringe. In some embodiments, providing a syringe
barrel includes forming a mounting structure at the rear end, the
mounting structure adapted for mounting the syringe to a pump: and
wherein attaching the restraining element includes attaching the
restraining element to the mounting structure. In some embodiments,
attaching a restraining element includes inserting the syringe into
a case and affixing a cap to the case; and wherein restraining
displacement of the plunger includes abutting the plunger against
the cap. In some embodiments, restraining displacement of the
plunger includes accommodating expansion of the freezing water
content with deflection of at least one of the plunger and
restraining element. In some embodiments, the method further
comprises permitting displacement of the plunger toward the
restraining element during freezing of the product-filled syringe,
prior to restraining displacement of the plunger with the
restraining element.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 illustrates an exemplary drug infusion system in
which the present invention may be used.
[0010] FIG. 2 illustrates a first syringe configuration in a filled
condition.
[0011] FIG. 3 illustrates the first syringe configuration in a
dispensing condition.
[0012] FIG. 4 illustrates the first syringe configuration with a
first alternative plunger.
[0013] FIG. 5 illustrates the first syringe configuration with a
second alternative plunger.
[0014] FIG. 6 illustrates the first syringe configuration with a
third alternative plunger.
[0015] FIG. 7 illustrates a second syringe configuration in a
filled condition.
[0016] FIG. 8 illustrates the second syringe configuration in a
dispensing condition.
[0017] FIG. 9 illustrates a third syringe configuration in a filled
condition.
[0018] FIG. 10 illustrates the third syringe configuration in a
dispensing condition.
[0019] FIG. 11 illustrates a fourth syringe configuration in a
filled condition.
[0020] FIG. 12 illustrates the fourth syringe configuration in a
dispensing condition.
[0021] FIG. 13 illustrates a fifth syringe configuration in an
initial filled position.
[0022] FIG. 14 is a bottom view of an end cap for use with the
fifth syringe configuration.
[0023] FIG. 15 is a side view of the end cap.
[0024] FIG. 16 illustrates a first step for installing the end cap
on the syringe.
[0025] FIG. 17 illustrates a second step for installing the end cap
on the syringe.
[0026] FIG. 18 illustrates a third step for installing the end cap
on the syringe.
[0027] FIG. 19 illustrates the fifth syringe configuration in an
initial accommmodation condition.
[0028] FIG. 20 illustrates the fifth syringe configuration in an
intermediate accommmodation condition.
[0029] FIG. 21 illustrates the fifth syringe configuration in a
final accommmodation condition.
[0030] FIG. 22 illustrates a sixth syringe configuration in an
initial condition.
[0031] FIG. 23 illustrates the sixth syringe configuration with the
plunger in a deflected condition.
[0032] FIG. 24 is an enlarged view of the restraining element of
the sixth syringe configuration.
[0033] FIG. 25 illustrates a seventh syringe configuration with the
plunger in a deflected condition.
[0034] FIG. 26 is a perspective view of the plunger for the seventh
configuration.
[0035] FIG. 27 is a rear end view of the syringe barrel of the
seventh configuration, with the plunger inserted.
[0036] FIG. 28 is rear end view of the syringe barrel of the
seventh configuration, with the plunger inserted and rotated.
[0037] FIG. 29 illustrates an alternative restraining element.
DETAILED DESCRIPTION
[0038] Before any embodiments of the invention are explained in
detail, it is to be understood that the invention is not limited in
its application to the details of construction and the arrangement
of components set forth in the following description or illustrated
in the following drawings. The invention is capable of other
embodiments and of being practiced or of being carried out in
various ways.
[0039] FIG. 1 illustrates a drug infusion system 10 that includes a
pump 15, a syringe 20, and a delivery tube 25 that can be inserted
into a patient's small intestine. The pump 15 actuates the syringe
20, which displaces product from the syringe 20 into the patient
through the tube 25. In many drug infusion systems, the pump 15
actuates the syringe in a slow, steady manner, such that the
patient receives the product at an optimal rate over an extended
period. The pump can be programmed to deliver the product at a
desired rate or according to a desired profile, and the program can
be modified in response to the patient's reaction to the
product.
[0040] The illustrated pump 15 is a portable pump, which can be
clipped to a patient's belt or otherwise carried by the patient as
the patient moves around. The pump 15 is powered by a portable
power source, which may include a single battery, a pack of
batteries or another form of portable power. The portable power
source will be referred to herein as the battery pack 27 for
convenience. In other embodiments, the power source for the pump 15
may be non-portable, such as, for example, a wall outlet and power
cord.
[0041] An example of a pump that is currently used for drug
infusion systems is the Cane Crono pump. Information regarding the
Cane Crono pump is available at the company's website
www.microjet.it. The Cane Crono pump is cited as merely one example
of a pump which can be used in a drug infusion system as
contemplated by the present invention. The findings and learnings
of the present invention can be applied to drug infusion systems
utilizing other pumps; the present invention should not be limited
to the specific system illustrated or described. The invention
involves advances in syringe design and should not be viewed as
limited to the application of a drug infusion system. A drug
infusion system is one environment in which such syringe design may
be used and is provided here as an example only.
[0042] One example of a product administered through a drug
infusion system is the Levodopa Carbidopa Intestinal Gel (LCIG)
sold under the trademark DUODOPA by Abbott Laboratories. LCIG is
used for treating patients with Advanced Parkinson's Disease. As
the name implies, LCIG is a gel. The gel is about ninety-six
percent (96%) water and therefore behaves much as water behaves
during phase changes. Other formulations of LCIG may include a
water content of about 94-95%, about 94.58%, or a water content of
at least 84%.
[0043] LCIG is typically filled into a syringe post-manufacture,
and the syringe and its contents are frozen and stored. Depending
on its specific composition, the LCIG may have a freezing
temperature of about -2.degree. C. (28.4.degree. F.). To ensure the
LCIG is solidly frozen, it may be exposed to and stored at
temperatures well below the freezing point. The syringes for LCIG
product must be gas tight during a two-year storage period and
during any shipping of the product. The storage and shipping
environment may be maintained, for example, at about negative
twenty degrees Celsius (-20.degree. C.) (-4.degree. F.) to ensure
the product is solidly frozen.
[0044] The syringe 20 must be free from leak paths (i.e., it must
be gas tight) during storage, shipping, thawing, and administering.
Thawing may be done in a refrigerator at about two degrees Celsius
to eight degrees Celsius (2.degree. C. to 8.degree. C.)
(35.6.degree. F. to 46.4.degree. F.), for example, prior to being
administered to a patient through the drug infusion system. To meet
the expected freezing, shipping, thawing, and administering
environments, the syringes should accommodate any temperatures and
ranges of temperatures between negative twenty-five and forty
degrees Celsius (-25.degree. C. to 40.degree. C.) (-13.degree. F.
to 104.degree. F.) while maintaining seal integrity (i.e., a
gas-tight seal that is free from leak paths). Within this range,
the syringes should remain gas tight during a phase change of the
gel from liquid to solid and from solid to liquid, which may occur,
for example, around -2.degree. C. (28.4.degree. F.). Expected
temperature ranges for the syringes include -20.degree. C. to
2.degree. C. (-4.degree. F. to 35.6.degree. F.), -20.degree. C. to
8.degree. C. (-4.degree. F. to 46.4.degree. F.), -20.degree. C. to
40.degree. C. (-4.degree. F. to 104.degree. F.), and -25.degree. C.
to 40.degree. C. (-13.degree. F. to 104.degree. F.). The syringes
should remain gas tight without regard to the rate of thawing.
[0045] Because of the high water content, the product expands as it
freezes, and contracts as it thaws. When a filled syringe is placed
at -20.degree. C., the gel expands about nine percent (-9%)
primarily in the axial direction and pushes the plunger outwards.
The stability of the product can be compromised upon mixing with
air, the addition of air to the gel may result in a decrease in
delivery accuracy of the product to the patient, and there is no
provision for the patient or care giver to remove air from the
product prior to administration. Consequently, the syringe must
accommodate expansion and contraction of the product without
permitting air to permeate through the various seals within the
syringe.
[0046] During the freeze-thaw cycle of a syringe with a
conventional, known plunger sealing arrangement, it was observed
that: there is a difference in thermal contraction between
thermoplastic material, such as polypropylene, and rubber
components; there are inadequate dimensions to provide sufficient
sealing between the plunger and the syringe barrel over a wide
temperature range (-25.degree. C. to 40.degree. C.); and the
plunger can tilt/cock/rack during freezing or thawing reducing seal
integrity. The result of these conditions leads to ingression of
air into the gel during the thaw cycle.
[0047] FIGS. 2 and 3 illustrate a first syringe 20 construction.
The syringe 20 includes a front end 30 and a rear end 35 and
defines a longitudinal axis 40 extending between the front and rear
ends 30, 35. Throughout this specification, the terms "front" and
"forward" refer to portions, elements, and directions close to or
in the direction of the front end 30 of the syringe 20, and the
terms "rear" and "rearward" refer to portions, elements, and
directions close to or in the direction of the rear end 35 of the
syringe 20. The terms "axial" and "axially" mean in a direction
parallel to the longitudinal axis 40 of the syringe 20, and the
terms "radial" and "radially" mean in a direction perpendicular to
the longitudinal axis 40.
[0048] The syringe 20 includes a barrel 45, a front o-ring 50, a
rear o-ring 55, and a plunger 60 (which may also be referred to as
a piston). The barrel 45 is made of thermoplastic material, such as
polypropylene. The barrel 45 is generally cylindrical, having an
outer surface 70 and an inner surface 75. The inner surface 75 of
the barrel 45 defines a barrel diameter 80. The barrel 45 includes
a reduced diameter portion 85, an enlarged diameter portion 90, and
a step or shoulder 95 between the reduced diameter portion 85 and
enlarged diameter portion 90. The step 95 may be longer and at a
shallower angle than illustrated. The barrel 45 includes an orifice
100 through which product is dispensed. The orifice 100
communicates with the tube 25.
[0049] The front o-ring 50 and rear o-ring 55 surround the plunger
60 and seal between the outside of the plunger 60 and the inner
surface 75 of the barrel 45. The rear o-ring 55 prevents or reduces
the likelihood of racking. Contact pressure arises between the
o-rings 50, 55 and the barrel 45 and between the o-rings 50, 55 and
the plunger 60. The contact pressure gives rise to friction.
Generally, the higher the contact pressure, the higher the
friction. Friction forces while the plunger 60 is at rest can be
referred to as static friction and friction forces while the
plunger 60 is moving can be referred to as gliding friction.
[0050] The seal between the o-rings 50, 55 and the barrel 45 is
gas-tight. The phrases "gas-tight," "gas-tightly," and variations
of these phrases, when used in reference to a seal in the present
disclosure, refer to the seal precluding the movement of air or
other gases from one side of the seal to the other side of the seal
in the presence of pressure gradients across the seal of a
magnitude experienced during thawing of the product within the
syringe as discussed herein, which may in some scenarios be on the
order of one atmosphere (1 atm), for example.
[0051] The plunger 60 is constructed of thermoplastic material,
such as polypropylene, and includes a front end having a contact
surface 120. A product chamber 125 is defined in the space in the
barrel 45 forward of the contact surface 120 and front o-ring 50.
The contact surface 120 faces and contacts the product within the
barrel 45. The o-rings 50, 55 create a sliding gas-tight seal
between the plunger 60 and the barrel 45. The plunger 60 moves
axially within the barrel 45 in a forward direction 130 and a
rearward direction 135 to decrease and increase, respectively, the
volume of the product chamber 125. The plunger 60 maybe said to
"advance" when moving in the forward direction 130 and "back up"
when moving in the rearward direction 135.
[0052] The relative thermal expansion coefficients of the materials
from which the barrel 45, plunger 60, and o-rings 50, 55 are made
will affect the relative changes in dimensions of the parts during
the freeze/thaw cycle. Generally, if the gap between the barrel 45
and plunger 60 increases during freezing, the contact pressure
between the o-rings 50, 55 and those components will reduce.
[0053] In the case of LCIG, or another product having high water
content, freezing the product-filled syringe 20 will cause the
product to expand as the water freezes. It will be understood that
in all constructions disclosed, a lure cap, well known in the art,
is threaded onto the syringe 20 over the orifice 100 so that
product cannot escape through the orifice. Expansion of the
product-filled syringe 20 will overcome the static friction of the
plunger 60 and force the plunger 60 rearward 135, which also
expands the volume of the product chamber 125. Expansion of the
product may also cause hoop stress in the barrel 45, which radially
expands the inner diameter 80 of the barrel 45. The product will
take the path of least resistance when expanding, however, so if
the static friction of the plunger 60 is low enough, there will be
minimal radial or circumferential expansion of the barrel 45
because the product will expand primarily in the axial
direction.
[0054] The syringe 20 and product will thaw radially inwardly from
the outer diameter of the barrel 45. As a consequence, the product
will contain an axially-extending column of ice that shrinks in
diameter as the product thaws. The column of ice extends from the
front end of the barrel 45 to the contact surface 120 of the
plunger 60. The column of ice resists movement of the plunger 60 in
the forward direction 130, which therefore resists or slows down
the shrinking of the volume of the product chamber 125 during
thawing. The portion of the product that thaws first (i.e., the
radial periphery of the product) will contract before the volume of
the product chamber 120 shrinks, which will give rise to pockets or
bubbles of vacuum within the thawed portion of the product.
[0055] Once thawed, the lure cap can be removed from the front end
30 and the syringe 20 is installed in the pump 15. The pump 15
includes a pushrod or other actuation element that is received in
the backside of the plunger 60. The pump 15 applies a linear force
on the plunger 60 through the pushrod to linearly displace the
plunger 60 in the forward direction 130 within the barrel 45 along
the longitudinal axis 40. The pump 15 must first overcome static
friction by applying a break-out force to the plunger 60, and then
must continually overcome gliding friction by maintain a sufficient
gliding force on the plunger 60 to keep the plunger 60 moving in
the forward direction 130. As the plunger 60 moves in the forward
direction 130, the volume of the product chamber 125 decreases and
product is forced out the orifice 100, through the tube 25, and
into the patient at a rate prescribed by the physician. The pump 15
draws power from the battery pack 27. The power drawn from the
battery pack 27 generally correlates to the force the pump 15
applies to the plunger 60.
[0056] The life of the battery pack 27 can be increased if the
required glide force is decreased. The syringe construction 20 in
FIGS. 2 and 3, and those below attempt to increase the life of the
battery pack 27 while providing a tight seal while the syringe is
full of product and going through the freezing and thawing cycle.
The syringe constructions in this specification provide relatively
high contact pressure while the syringe is full, and a lower
contact pressure after a predetermined amount of product have been
dispensed.
[0057] The plunger 60 and o-rings 50, 55 are inserted into the
barrel 45. Then the plunger 60 is pulled rearwardly 135 to draw the
product into the product chamber 125 through the orifice 100. The
plunger 60 and both o-rings 50, 55 are within the reduced diameter
portion 85 when the syringe 20 is full. When the syringe 20 is
frozen, the product expands, which pushes the plunger 60 rearwardly
135 in the barrel 45. The reduced diameter portion 85 is
sufficiently long so that the plunger 60, and more specifically, at
least the front o-ring 50, stays within the reduced diameter
portion 85 as the plunger 60 backs up in the barrel 45 as the
product is frozen.
[0058] As discussed above, when it is time to dispense the product,
the syringe 20 and its contents are thawed. There is a higher
contact pressure on the o-rings 50, 55 arising from the plunger 60
being in the reduced diameter portion 85 during freezing and
thawing. The higher contact pressure accommodates the gap between
the plunger 60 and barrel 45 increasing during the freezing and
thawing cycle, while maintaining a gas-tight seal throughout. This
reduces the likelihood that air will be drawn around the o-rings
50, 55 and into the product chamber 125.
[0059] Once the product is thawed, the pump 15 pushes on the
plunger 60 with the break-out force to overcome the static friction
arising from the o-rings 50, 55 sealing against the reduced
diameter portion 85. Once the o-rings 50, 55 cross the step 95 and
enter the enlarged diameter portion 90, the contact pressure
decreases, and the required glide force is reduced so that less
power is required to push the plunger 60 forward 130. This
conserves energy and increases the life of the battery pack 27.
[0060] The shoulder 95 is positioned in the barrel such that the
o-rings 50, 55 cross into the enlarged diameter portion 90 when the
product chamber has a volume of about 45 mL (i.e., 45 mL of product
in the syringe 20). In this example, if the syringe 20 is provided
with 50 mL of product when full, the pump must overcome the higher
contact pressure of the o-rings 50, 55 in the reduced diameter
portion 85 while dispensing the first 5 mL of product. Stated
another way, pump 15 only has to overcome the higher contact
pressure and sealing forces while dispensing the first 10% of the
product, and then overcomes the lower contact pressure and sealing
forces while dispensing the remaining 90% of the product.
[0061] This arrangement can be said to have a barrel with first and
second portions (i.e., the reduced diameter portion 85 and the
enlarged diameter portion 90). One or both of the o-rings 50, 55
being a sealing member that engages the first portion with a first
contact pressure and that engages the second portion with a second
contact pressure that is lower than the first contact pressure.
Consequently, a first force is required to break out the plunger
from the first portion and a second force, lower than the first
force, is required to slide the plunger in the second portion. This
two-stage sealing arrangement carries through all constructions and
embodiments described in this specification, and provides a
relatively tight seal when the syringe is full and the syringe goes
through the freezing and thawing cycle through the expected
temperature range of -25.degree. C. to 40.degree. C. A relatively
loose seal is provided when the plunger is moved within the barrel
to dispense product.
[0062] FIGS. 4, 5 and 6 illustrate alternative versions of the
plunger for use in the present invention. These alternative
versions are provided as examples only, and are not limiting. In
FIG. 4, the plunger 160 includes an overmolded seal 170 over the
front end of the plunger 160. The overmolded seal 170 provides a
sealing rim 150 that performs the same function as the front o-ring
50 of the first plunger 60. The overmolded seal 170 in this
construction provides the contact surface 120 and defines a portion
of the product chamber 125. The plunger 160 also includes the rear
o-ring 55 in this example, to prevent racking.
[0063] In FIG. 5, the plunger 260 is covered with an overmolded
seal 270 that includes front and rear sealing rims or wipers 250,
255 that perform the same function as the respective front and rear
o-rings 50, 55 of the first construction. The overmolded seal 270
defines the contact surface 120 and defines a portion of the
product chamber 125.
[0064] FIG. 6 illustrates a plunger 360 having wipers 350, 355 in
place of the o-rings 50, 55. The wipers 350, 355 resiliently engage
and slide against the inner surface of the syringe barrel 45.
Because the wipers 350, 355 are swept back (rearward), they may
engage or catch on the step 95 in the barrel 45 after they have
moved forward of the step 95 and the plunger 360 backs up. For the
plunger 360 to back up rearward of the step 95, the wipers 350, 355
will need to double over, fold, or collapse. The wipers 350, 355
will in many configurations provide more resistance to the plunger
360 backing up over the step 95 than the resistance provided by the
o-rings 50, 55 and overmolded seals 170, 270. Because of their
generally circular or part-circular cross-sections, the o-rings 50,
55 and sealing rims 150, 250, 255 of the overmolded seals 170, 270
include rounded rearward-facing surfaces which will offer some
resistance to the plunger 360 backing up over the step 95, but
typically not as much resistance as offered by the wipers 350,
355.
[0065] It will be understood that plungers 160, 260, 360 are
examples of the many different configurations of plungers can be
used with the present invention, and that all such variations are
contemplated for all syringe constructions disclosed herein. It
will be understood that the function of the o-rings 50, 55 of the
first exemplary plunger 60 is replaced with the sealing rims or
wipers 150, 250, 255, 350, 355 of the other plungers 260, 360, and
such sealing rims and wipers can be substituted for the o-rings 50,
55 in the following examples as well, where appropriate.
Combinations of the o-rings 50, 55, overmolded seals 170, 270, and
wipers 350, 355 can be employed as well. For example, one o-ring 50
or 55 and one wiper 350, 355 can be used in combination on the
plunger, or the wiper 355 can be used in place of the rear o-ring
55 with the overmolded seal 170. One of ordinary skill in the art
will appreciate all permutations of the various sealing
arrangements disclosed herein and apply them to the best advantage
in a given syringe arrangement. One of ordinary skill in the art
will also factor into the selection of the sealing configuration
whether it is desirable to have more or less resistance to the
plunger backing up past the step in the barrel or any other rim or
lip in the barrel other than the illustrated step.
[0066] FIGS. 7 and 8 illustrate a second syringe configuration that
includes a syringe 420. The syringe 420 includes a barrel 445, and
the above-described front o-ring 50, rear o-ring 55, and plunger
60. The barrel 445 is in all respects the same as barrel 45
described above, except that step 95 is moved rearward. When the
syringe 420 is full of product, the front o-ring 50 is forward of
the step 95 and the rear o-ring 55 is rearward of the step 95. The
rear o-ring 55 is exposed to high contact pressure and provides a
tight seal during the freeze-thaw cycle. The syringe 420 is filled
with product in the product chamber 125 and frozen, as discussed
above. The front o-ring 50 (or any other type of seal used in place
of the front o-ring 50) engages the step 95 to resist rearward
movement of the plunger 60 as the product is frozen.
[0067] Only a relatively small amount of product needs to be
dispensed before the rear o-ring 55 crosses the step 95. In one
example, if the syringe 420 is full at 50 mL, only about 2 mL needs
to be dispensed (i.e., the product chamber 125 is at 48 mL) before
the rear o-ring 55 has crossed the step 95. Stated another way,
pump 15 only has to overcome the higher contact pressure and
sealing forces while dispensing the first 4% of the product, and
then overcomes the lower contact pressure and sealing forces while
dispensing the remaining 96% of the product. Battery life can be
improved with this construction because only a single o-ring 55
gives rise to higher contact pressure and static friction when the
syringe 420 is full, and both the front and rear o-rings 50, 55 are
within the large diameter portion of the syringe 420 after
dispensing relatively little product.
[0068] FIGS. 9 and 10 illustrate a third syringe configuration that
includes a syringe 520. The syringe 520 includes a barrel 545, a
front wiper 550, the rear o-ring 55, and a plunger 560. The barrel
545 is similar to barrel 45 described above in all respects, except
that the shoulder 95 is more pronounced and moved rearwardly
compared to the barrel 45. The rear o-ring 55 fits tightly between
the plunger 560 and the reduced diameter portion 85 to give rise to
high contact pressure and air-tight sealing during the freeze-thaw
cycle.
[0069] The plunger 560 includes a rigid core that is generally
cylindrical and of an outer diameter smaller than the reduced
diameter portion 85 so that it can move axially through the reduced
diameter portion 85. The front wiper 550 is interconnected to the
front end of the plunger 560 and contacts the inner surface 75 of
the syringe barrel 545 in the enlarged diameter portion 90. The
wiper 550 is flexible enough to deflect as the front end of the
plunger 560 is pushed through the reduced diameter portion 85 as
the plunger 560 is installed in the barrel 545, and then
resiliently expand within the enlarged diameter portion 90 to
create a seal for the product chamber 125.
[0070] The rear o-ring 55 creates an airtight seal between the
plunger 560 and the reduced diameter portion 85. The seal between
the wiper 550 and the enlarged diameter portion 90 is preferably
also air-tight, but it is less critical that this seal be airtight
than the rear seal 55. An annular chamber 580 is defined around the
plunger 560 between the rear side of the wiper 550 and the rear
o-ring 55 when the syringe 520 is filled. The chamber 580 can be
evacuated and filled with inert gas when the product chamber 125 is
filled with product. Unlike air, the inert gas will not degrade the
product in the product chamber 125 if it migrates past the wiper
550.
[0071] The syringe 520 is filled with product in the product
chamber 125 and frozen, as discussed above. The free edge of the
wiper 550 engages the step 95 to resist rearward movement of the
plunger 560 as the product is frozen and the plunger 560 attempts
to back up.
[0072] The seal between the wiper 550 and the inner surface 75 of
the barrel 545 may have relatively low contact pressure, such that,
as the product is thawed, the inert gas in the chamber 580 may be
drawn into the product chamber 125. The wiper 550 creates a seal
between the plunger 560 and the barrel 545 sufficient to prevent
any substantial volume of product to escape rearwardly around the
plunger 560 as the product is dispensed.
[0073] As illustrated in FIG. 10, when the plunger 560 has been
advanced sufficiently (e.g., 2 mL) to move the rear o-ring 55
across the step 95, the contact pressure between the rear o-ring 55
and the reduced diameter portion 85 drops to zero, and the rear
o-ring 55 does not seal against the barrel 545 at all. Once the
rear o-ring 55 is disengaged from the reduced diameter portion 85,
the only frictional force against the inner surface of the barrel
545 arises from the wiper 550. Once the rear o-ring 55 is
disengaged, gliding friction is reduced substantially compared to
the static and gliding friction when the syringe 520 is full.
[0074] FIGS. 11 and 12 illustrate a fourth construction 620 of the
syringe. The syringe 620 includes a barrel 645, the front o-ring
50, the rear o-ring 55, a plunger 660, and an insert 665. The
plunger 660 includes a front portion 660a, having an enlarged head,
and a rear portion 660b.
[0075] The barrel 645 is generally cylindrical. The insert 665 is
inserted into the open rear end of the barrel 645. The barrel 645
and insert 665 define the reduced diameter portion 85 (within the
insert 665), the enlarged diameter portion 90 (within the barrel
645), and the step or shoulder 95 defined by the front end of the
insert 665 between the reduced diameter portion 85 and enlarged
diameter portion 90.
[0076] The plunger 660 is inserted into the barrel 645, then the
insert 665 is fit within the open rear end of the barrel 645 behind
the plunger 660. The insert 665 may be rigidly and permanently
affixed to the barrel 645, as by welding or with an adhesive, or
may be threaded into the open end of the barrel 645, provided that
the interconnecte between the insert 665 and the barrel 645 is air
tight. Product is drawn into the product chamber 125 by drawing the
plunger 660 rearward. The rear o-ring 55 creates an airtight seal
between the rear portion 660b of the plunger 660 and the reduced
diameter portion 85. The seal between the front a-ring 50 and the
enlarged diameter portion 90 is preferably also air-tight, but it
is less critical that this seal be airtight than the rear seal
55.
[0077] An annular chamber 680 is defined around the plunger 660
between the front and rear o-rings 50, 55 when the syringe 620 is
filled. The chamber 665 can be evacuated and filled with inert gas
when the product chamber 125 is filled with product. Unlike air,
the inert gas will not degrade the product in the product chamber
125 if it migrates past the front o-ring 50.
[0078] The syringe 620 is frozen with the product chamber 125
filled with product, as discussed above. The front portion 660a of
the plunger 660 engages the step 95 to resist rearward movement of
the plunger 660 as the product is frozen and the plunger 660
attempts to back up.
[0079] The seal between the front o-ring 50 and the inner surface
of the barrel 645 may have relatively low contact pressure, such
that, as the product is thawed, the inert gas in the chamber 680
may be drawn into the product chamber 125. The front o-ring 50
creates a seal between the plunger 660 and the barrel 645
sufficient to prevent any substantial volume of product to escape
rearwardly around the plunger 660 as the product is dispensed.
[0080] As illustrated in FIG. 12, when the plunger 660 has been
advanced sufficiently (e.g., 2 mL) to move the rear o-ring 55
across the step 95, the contact pressure between the rear o-ring 55
and the reduced diameter portion 85 drops to zero, and the rear
o-ring 55 does not seal against the barrel 645 at all. Once the
rear o-ring 55 is disengaged from the reduced diameter portion 85,
the only frictional force against the inner surface of the barrel
645 arises from the front o-ring 50. As a result, the rear o-ring
55 is entirely disengaged and gliding friction is reduced
substantially compared to the static and gliding friction when the
syringe 620 is full.
[0081] The above constructions and embodiments provide a method for
storing and dispensing a product having a high content of water. In
each construction a syringe barrel is provided that has a first
portion with a first inner diameter and a second portion with a
second inner diameter that is larger than the first inner diameter.
A plunger is inserted into the barrel and the syringe is filled
with product, such that the plunger is positioned within the first
portion of the barrel. A sealing member of the plunger engages the
first portion of the barrel to give rise to a first contact
pressure when the barrel is filled with product. The sealing member
may include first and second sealing members, both of which may be
positioned in the first portion of the barrel when the syringe is
full, or one of which may be positioned in the first portion and
the second of which may be positioned in the second portion of the
barrel when the syringe is filled with of product. The first
contact pressure is sufficient to maintain a gas-tight seal over
the expected temperature ranges -25.degree. C. to 40.degree. C. A
first force is applied to the plunger to overcome the first contact
pressure and move the plunger out of the first portion and into the
second portion to dispense product. The sealing member engages the
second portion of the barrel to give rise to a second contact
pressure that is lower than the first contact pressure. A second
force lower than the first force is sufficient to overcome the
second contact pressure and move the plunger in the second portion
to continue dispensing product.
[0082] FIGS. 13-18 illustrate a fifth construction 720 of the
syringe. The syringe 720 includes a barrel 745 and a plunger 760.
The barrel 745 includes a pair of radial flanges 740 on the rear
end. The radial flanges 740 may be used to mount the syringe 720
into certain types of pumps 15, such as the Cane Crono pump
discussed above. Other mounting structure than the radial flanges
740 may be employed, depending on the type of pump 15.
[0083] The plunger 760 (which may also be called a piston) is made
of resilient rubber, and includes an integral front sealing member
750 and an integral rear sealing member 755. The plunger 760 is a
standard, commercially available rubber component.
[0084] Referring to FIGS. 14 and 15, the assembly further includes
an end cap 765. The end cap 765 includes a top 770 and a pair of
engaging elements 775. When viewed from the side (FIG. 15), the
engaging elements 775 are c-shaped and each defines a channel 780.
The engaging elements 775 are diametrically opposed and define
between their ends diametrically aligned slots 785 that are wider
than the flanges 740 of the syringe 720.
[0085] With reference to FIGS. 16-18, the end cap 765 is installed
on the syringe 720 by positioning the flanges 740 in the slots 785
as illustrated in FIGS. 16 and 17, and then rotating the end cap
765 and syringe 720 with respect to each other about the axis 40 so
that the flanges 740 slide into the channels 780, as illustrated in
FIG. 18. This insert-and-twist assembly process for the end cap 765
is commonly referred to as a bayonet configuration. In other
configurations, the end cap 765 is designed to be affixed to
whatever mounting structure the syringe includes, which may be the
flanges 740 or another structure.
[0086] The present invention provides several modes of
accommodating the expansion of the product in the syringe as the
water content expands duringe freezing, without compromising at
least one of the front and rear seals on the piston and while
preventing the piston from racking in the syringe barrel. These
modes of accommodation are in addition to slight deflection of the
syringe barrel, which may occur, but is not desirable because of
the negative affect it may have on the seal between the plunger the
barrel.
[0087] A first mode of accommodating expansion of the product is
illustrated in the sequence of FIGS. 18-19. In FIG. 18, there is
space between the plunger 760 and the end cap 765. Expansion of the
product pushes or displaces the plunger 760 rearward until the
plunger 760 engages the end cap 765. Such displacement is a first
mode of accommodating expansion of the product. This first mode of
accommodation is also present in all previously-described
configurations (FIGS. 2-12).
[0088] A second mode of accommodating expansion of the product is
illustrated in the sequence of FIGS. 19-20, in which the plunger
760 is pressed against the end cap 765. When force on the end cap
765 exceeds a restraining element deflection threshold, the end cap
765 deflects or bulges. The deflection of the end cap 765
accommodates further expansion of the product.
[0089] A third mode of accommodating expansion of the product is
illustrated in the sequence of FIGS. 20-21, in which force on the
plunger 760 exceeds a plunger deflection threshold. When the force
exceeds the plunger deflection threshold, the plunger deflects.
[0090] The aspect of the invention directed to accommodating
expansion of the product during freezing does not necessarily
require all three modes of accommodation, it is possible to
configure the syringe assembly to only require any one or two of
the three modes. The end cap deflection and plunger deflection may
be resilient or non-resilient. In other words, the components may
return to their original shape as the load is removed during
thawing, or the components may remain deflected. Through design of
the components and selection of materials, the restraining element
deflection threshold may be higher or lower than the plunger
deflection threshold, so it is possible to design the assembly such
that the plunger deflects prior to (at a lower force than) the
cap.
[0091] This second and third modes of accommodation, or either
mode, may also be present in all previously-described
configurations (FIGS. 2-12) if an end cap or other restraining
element is installed on the syringe and if the plunger is designed
to deflect. For example, the third mode of accommodating expansion
(plunger deflection) may be designed into the configurations of
FIGS. 9-10 and 11-12.
[0092] In FIGS. 9-10, the wiper 550 may deflect once the plunger
deflection threshold is exceeded, a portion of the plunger 560 may
deflect, or both the wiper 550 and a portion of the plunger 560 may
deflect, In FIGS. 11-12, a portion of the plunger 660 may be
designed to deflect upon a plunger deflection threshold being
exceeded. As a further analogy between the configurations of FIGS.
9-10, 11-12, and 13-18, the shoulder 95 provided by the syringe
barrel 545 in FIGS. 9-10 and by the insert 665 in FIGS. 11-12, and
the end cap 765 of FIGS. 13-18 may be broadly referred to as
restraining elements, which restrain rearward movement of the
plunger at some point.
[0093] FIGS. 22-24 illustrate a sixth syringe configuration 820,
having a barrel 845 and a plunger 860 similar to the barrel 745 and
plunger 760 of the fifth configuration 720 of FIGS. 13-18. The
plunger includes a front sealing member 850 and a rear sealing
member 855, similar to the front and rear sealing members 750, 755
above. In this configuration, the barrel 845 includes an inwardly
extending radial restraining element in the form of a ring 865. As
seen in FIG. 24, the ring 865 includes a rear face 870 and forward
face 880 that may be slanted. The rear face 870 is slanted or
angled such that the front and rear sealing members 850, 855 can
slide past the ring 865 with resilient deflection of the plunger
860. The forward face 880 is slanted or angled (or perpendicular to
the syringe barrel wall) such that rearward movement of the plunger
760 is arrested and resisted upon the rear sealing member 855
engaging the forward face 880. The ring 865 resists rearward
movement of the plunger and forces in excess of the plunger
deflection threshold. The head of the plunger 860 will accommodate
expansion of product during freezing by deflecting as seen in FIG.
23.
[0094] FIGS. 25-28 illustrates a seventh syringe configuration 920,
having a barrel 945 and a plunger 960 similar in many respects to
the fifth and sixth configurations described above. The barrel 945
includes a flange 940 at the rear end. The flange 940 overhangs the
inner chamber of the syringe barrel 945, with the exception of a
pair of diametrically-opposed slots 950 (FIGS. 27, 28). Referring
to FIG. 26, the plunger includes a pair of diametrically-opposed
lugs 970. The lugs 970 may be integrally molded with the plunger
960 or may be installed after the plunger 960 is molded. In one
configuration, the lugs 960 may be integrally formed with a ring
that snaps into a circumferential groove around the plunger 960. As
illustrated in FIGS. 27 and 28, the plunger 960 fits into the
syringe barrel 945 with a bayonet configuration. More specifically,
as illustrated in FIG. 27, the lugs 970 of the plunger 960 pass
through the slots 950 in the flange 940 as the plunger 960 is
inserted into the rear end of the barrel 945. Once the plunger 960
is in the barrel 945, with the lugs 970 having cleared the flange
940, the plunger 960 is rotated about the longitudinal axis 40 as
shown in FIG. 28, such that the lugs 970 are under the flange 940.
The lug 970 and flange 940 engagement resists rearward movement of
the plunger 960 and racking of the plunger 960, and in this regard
the flange 940, plunger 960, or both may be called the restraining
element in this configuration. In FIG. 25, the plunger 960 is shown
in the deflected condition, the plunger 960 and its lugs 970 having
been forced against the flange 940 with a force in excess of the
plunger deflection threshold.
[0095] FIG. 29 illustrates an alternative restraining element for a
syringe configuration similar to the fifth syringe configuration
720, so the same reference numbers will be used. The alternative
restraining element includes a case 1010 into which the syringe 720
is inserted. The bottom of the case 1010 may include a stopper
element 1015 that plugs the orifice 85 at the front end of the
syringe 720, thereby performing the function of a lure cap. The
case 1010 may include male threads 1020 or other connecting
mechanism. The restraining element also includes a cap 1025 that
interconnects to the case 1010 via the threads 1020 or other
connecting mechanism. In this version of the restraining element,
the case 1010 and the cap 1025 are dimensioned so that the cap 1025
is held at a desired position (e.g., across the rear end of the
syringe 720) to restrain displacement of the plunger 760. As the
plunger 760 bears against the cap 1025, the front end of the
syringe 720 bears against the bottom of the case 1010. The case
1010 and cap 825 surround the syringe 720 and protect it from
light.
[0096] Thus, the invention provides, among other things, a
gas-tight sealing arrangement for a plunger of a syringe, and a
method for storing and dispensing product in such a syringe that
includes freezing and thawing the syringe and product while
maintaining the gas-tight sealing arrangement throughout the
process. The invention also provides methods and apparatus for
accommodating expansion of freezing water in the product contained
in the syringe. Such methods include rearward displacement of the
plunger, deflection of a portion of the plunger, deflection of a
restraining element, or a combination of one or more of these
methods. The apparatus includes a step in the syringe barrel, an
end cap affixed to the rear end of the syringe barrel, a case
surrounding the syringe, or another form of restraining element.
Various features and advantages of the invention are set forth in
the following claims.
* * * * *
References