Note: Descriptions are shown in the official language in which they were submitted.
. . 2196316
iW0 96104031 PCTlUS95108719
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SYRTNG~ WT'T'H CANNULA-PROTECTING SHEATH
AND SEALING CENTER ROD
O
The present invention pertains to a syringe of
the type that is prefilled/with a substance for both
storing the substance within the syringe and later
ejecting the substance from the syringe, e.g., to
inject the substance into the body of an animal. The
syringe is comprised of a plunger, a syringe barrel,
a cannula projecting from one end of the barrel or
a
cannula collar affixed thereto, and a removable
sheath attached to the syringe barrel and covering
the cannula to shield it from contamination and/or
unwanted contacts prior to desired ejection of the
substance from the syringe. A center bore extends
through the cannula to the interior chamber of the
syringe barrel. At least a segment of the bore
changes (e.g., tapers) to a smaller diameter in the
direction extending from the cannula distal end to
the interior chamber of the syringe barrel. The
sheath has a center rod affixed thereto that extends
axially from the sheath through the cannula and seats
in a sealing engagement with at least said segment
of
the interior bore, sealing the substance within the
syringe barrel interior chamber until such time as
ejection is desired.
The syringe of this invention has various
advantages in addition to the cannula-shielding
feature mentioned above. These advantages include
greater ease of use, compared to commonly used
techniques such as (1) affixing a cannula to a
prefilled syringe barrel before injecting the
substance through the cannula and (2) draw-up of the
injectable substance through a pre-attached cannula
into the syringe barrel from which it isexpelled
during a subsequent injection. Other important
.
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advantages of the aforementioned sealing engagement
are that it (1} prevents leakage of the substance
r
from the syringe barrel intothe sheath during
storage of the syringe and (2} prevents any solid
particles which settle or precipitate out of the
substance stored in the syringe from accumulating in
the cannula and then clogging or restricting flow of
the substance through the cannula at the time of
desired injection.
l0
I?ESCRIFTION OF THE RELATED ART
There are various kinds of known prefilled
syringes, e.g., those having interior chambers that
store a substance prior to its ejection from the
syringe. Prefilled syringes are often,used where a
large number of injections are to be made in as short
a time period as possible and with as little
difficulty as possible. Syringes of this type have
found uses in injecting praphylactic, therapeutic and
stimulative substances.
One example of a beneficial use of prefilled
syringes is in injecting herds of livestock. For
example, in a dairy herd containing many animals, use
of prefilled syringes where each is used to inject a
measured dose of a substance into one animal of the
herd enables the injections of the herd to take place
with a considerable savings of time and effort.-
To reduce the cost of the disposable, prefilled
syringes, they typically have a simple construction
and are comprised of a syringe barrel with an
interior chamber, a plunger inserted into the chamber
at one end of the barrel, a cannula extending from
the opposite end of the barrel, and in some instances
a cannula cap or sheath. Over time, when particular
substances are stored in the conventional syringe
described above, for example a substance containing
solids or particulate matter suspended or dissolved
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Y
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in a liquid or gel, the solids may settle out or
precipitate in the form of particles that can collect
in the interior bore of the cannula and clog the
thus preventing or restricting delivery of the
bore
,
substance through the cannula when that is desired,
e.g., when the syringe plunger is pushed through the
syringe barrel=interior chamber to eject the
substance from-the syringe.
Certain prior art syringes have been constructed
with rods extending through the center of the syringe
cannula, some with a cap on the rod that seats over
the cannula tip to prevent the substance stored in
the syringe from leaking prematurely from the
cannula. However, these prior art rods have been
generally constructed with a diameter smaller than
the diameter of the cannula bore. No steps have been
taken to seal the cannula interior bore from the
barrel interior chamber, even with the rod inserted
through the bore. With such prior art devices, there
is an undesirable potential for solid particles to
settle or precipitate out of the substance stored in
the syringe interior chamber and leak into and become
lodged within the cannula, i.e.,. within the space
between the interior bore of the cannula and the
surface of the rod inserted in the interior bore.
Although removal of the rod from the cannula will
provide a flow path through the interior bore for the
substance contained in the syringe interior chamber,
solid particles that have settled or precipitated out
of the substance and have become lodged along the
' interior surface of the cannula bare will slow and/or
partially restrict the flow of the-.substance through
the cannula bore as the syringe plunger is pushed to
eject the substance from the syringe interior
chamber.
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SUMMARY OF THE INVENTION
In accordance with one embodiment of the present
invention there is provided in a syringe that is prefilled
with a substance for both storing the substance within the
syringe and later ejecting the substance from the syringe,
the improvement comprising: a syringe barrel having an axial
length with a cannula collar at one end of the barrel length
and an interior chamber within the barrel; a hollow cannula
having axially opposite proximal and distal ends, the
proximal end being secured to the syringe barrel collar with
the cannula extending axially from the collar to its distal
end; a bore having a length extending axially through the
cannula and the syringe barrel collar between the cannula
distal end and the syringe barrel interior chamber, the bore
having an interior surface where at last a segment of the
length of the bore changes in diameter from a first interior
diameter of the bore to a second interior diameter of the
bore, less than the first interior diameter, as the bore
extends in the direction from the cannula distal end to the
barrel interior chamber through the bore segment; and, a
center rod removably inserted axially into the bore at the
cannula distal end and seating in a sealing engagement with
said segment of the interior bore.
The syringe of this invention is constructed with a
syringe barrel having a hollow interior chamber. Generally,
a cannula collar is provided at one end of the barrel and a
plunger extends into the interior chamber at the opposite
end of the barrel. The cannula is secured to the syringe
barrel collar, and in a preferred embodiment is seated on a
shoulder (e.g., circular) of the collar which prevents the
cannula from being pushed into the syringe barrel, e.g.,
when a force is exerted on the distal end of the cannula
when an injection is initiated. A hollow interior bore
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extends axially through the center of the cannula and
through the syringe barrel collar as it extends from the
cannula tip to the syringe barrel interior chamber.
Generally, a first segment of the interior bore has a
substantially constant interior diameter as it extends
through the length of the cannula. Normally, a second
segment of the interior bore tapers to a smaller diameter,
e.g., as it extends through the syringe barrel collar,
although the decrease in diameter can be abrupt, if desired,
rather than gradual. In a preferred embodiment, the second
segment tapers from a first interior diameter that is
substantially equal to the interior diameter of the bore
within the cannula, to a second, smaller interior diameter
of the bore segment at the exit of the bore into the syringe
barrel interior chamber.
A sheath is attached removably (e.g., by force fit of a
sheath made of a resilient material) to the syringe barrel
and essentially completely covers the cannula. The sheath
has a center rod affixed to the sheath in the sheath
interior. The center rod is removably inserted into the
bore at the cannula distal end and preferably, but not
necessarily.
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R 96/04031
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extends through the complete
length of the bore while
thesheath is attached to the
syringe barrel.
In a preferred embodiment, the
center rod has a
substantially constant exterior
diameter along its
length. The rod diameter is smaller
than the
interior diameter of the first
segment of the bore,
and is larger than the interior
diameter of the
second segment of the bore. Thus,
as the center rod
is inserted into and through
the interior bore, the
rod wedges within the bore at
the location where the
interior diameter of the bore
becomes (e. g., tapers
to) less than that of the rod,
thus producing a
seal.
Preferably, both the syringe
barrel collar and
the sheath center rod are constructed
of resilient
plastic materials) that compresses)
slightly as the
rod is wedged~into the smaller-diameter
segment of
the bore, thereby providing a
sealed engagement of
the rod with that segment of
the bore. This sealed
engagement between the rod and
thesecond segment of
the bore is most desirably situated
at the opening of
the bore to the syringe barrel
interior chamber,
preventing-any of the substance
contained in the
chamber from entering the bore
until the rod is
removed from the cannula.
BRIEF DESCRIPTION OF THE DRAWINGS
Further objects and features
of the present
invention are revealed in the
following detailed
description of the preferred
embodiment of the
invention and in the drawing
figures wherein:
Figure 1 is a side elevation
view of the sheath
and syringeof the present invention;
Figure 2 is a partial view, in
section, showing
detail of the sheath and syringe
of the invention;
Figure 3 is a partial view, in
section, taken in
a plane along the line 3-3 of
Figure 2; and,
W096I04031 219 6 316 PCT/US95I08719
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Figure 4 is a partial view, in section, similar
to that of Figure 3 showing the sheath center rod
,.
withdrawn from the tapered portion of the syringe
bore.
r
nccrnrymTON OF THE PREFERRED EMBODIMENTS
The syringe 10 of 'the present invention is shown
assembled in Figure d. Basically, the syringe 10 is
comprised of a syringe plunger 12, a syringe barrel
14 and a protective sheath 16. In the preferred
embodiment of the invention, these basic component
parts are all constructed of a resilient, plastic
material, for- example polyethylene or polypropylene.
Plunger 12 is slidably received within the barrel 14,
and sheath 16 is removably attached to the end of
barrel 14. Plunger 12-includes an elongated rod 22
with a finger push tab 24 at one end and a sealing
piston 26 at its opposite end (shown in Figure 2).
The syringe barrel 14 has a cylindrical, tubular
configuration with finger flanges 32 at one end and a
cannula collar 34 at the axially opposite end of the
elongated barrel 14. The interior chamber 36 of the
barrel has a cylindrical interior surface dimensioned
to receive the plunger piston 26 in sliding, sealing
engagement therein.
The cannula 38 is supported in the cannula collar
34 of the syringe. The cannula 38 has an axial
length with opposite proximal 42 and distal 44 ends.
The proximal end 42 is secured within the collar 34
of the syringe barrel 14 by an adhesive 46 or-in some
other suitable manner. The cannula distal end 44
outside the collar 34 tapers to a sharpened end,
e.g., a point. Typically, the cannula is constructed ,.
of a metal (e. g., stainless steel) and is from about
10 to about 18 (preferably about 16) gauge. The
cannula has a cylindrical interior.surface 48 that
surrounds an interior bore 52 of the syringe, the
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interior bore 52 extending from the cannula distal
end 44 through the cannula 38 and the collar 34 to
the syringe barrel interior chamber 36.
The segment of the interior bare 52 that extends
through the cannula between its distal 44 and
proximal 42 ends has a constant interior diameter.
The segment of the interior bore 52 that extends from
the cannula proximal end 42 through the syringe
collar 34 to the barrel interior chamber 36 tapers as
it extends toward the interior chamber. This segment
of the interior bore 52 is surrounded by an interior
surface 54 of the syringe barrel collar 34 having a
frustoconical configuration. As in Figures 3 and 4,
the segment of the interior bore 52 surrounded by the
collar interior surface 54 begins with an interior
diameter substantially equal to that of the cannula
interior surface 48 and tapers to an interior
diameter less than that of the cannula interior
surface as it extends toward the interior chamber 36
of the syringe barrel from the cannula proximal end
42.
The sheath 16 has an axial length with a hollow
interior 62. A collar 64 surrounds an opening to the
interior at one end of the sheath and the opposite
end 66 of the sheath is closed. The collar 64 is
configured to be releasably attached around the
exterior of the syringe barrel 14 adjacent the collar
34, as in Figure 2. The sheath interior 62 is
sufficiently large to receive the syringe barrel
collar 34 and the cannula 38 therein with the collar
64 removably attached over the exterior of the
syringe barrel 14 as shown in Figure 2. A center
rod 68 is affixed to the sheath 16 within its
interior 62. The centex.ro~ 68 has an elongated
configuration with a distal end 72 secured to the
closed end 66 of the sheath and a proximal end 74
positioned outside the sheath interior 62. As seen
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.g,
in Figure 2, the length of the rod is sufficient to
project the rod proximal end 74 completely through the
tapered segment of the interior bore 52 within the
syringe barrel collar 34 with the sheath 16 attached
to the exterior of the syringe barrel.
In a preferred embodiment of the invention, the
center rod 68 has a cylindrical configuration with a
constant diameter along its entire length. The
diameter of the center rod 68 is less than the
interior diameter of the segment of the interior bore
52 surrounded by the cannula interior surface 48, but
is larger than the interior diameter of at least a
portion of the segment of the interior bore 52
surrounded by the interior surface 54 of the syringe
barrel collar 34. With these relative diameter
dimensions of the sheath center rod 68 and the
tapered segment of the interior bore 52 extending
through the syringe barrel collar 34, at least
portions of both the segment of the interior bore 52
extending through the syringe collar 34 and the
sheath center rod 68 adjacent its proximal end 74 will
compress when the rod 68 is inserted through the
interior bore 52 and the sheath collar 64 is attached
to the exterior of the syringe barrel 14 in the
position shown in Figure 2. This compression of both
the collar interior surface 54 and the sheath center
rod 68 produces a sealing engagement between the
collar surface and center rod.
In a variant embodiment of the center rod 68, a
portion of the rod adjacent its proximal end 74 may be
tapered slightly as shown in phantom lines in Figure
3. The taper is provided to assist in insertion of
the rod proximal end 74 through the interior bore 52 at
the cannula distal end 44 when attaching the sheath
to the syringe barrel exterior. Such a taper of the
end of rod 68 is especially advantageous if the
diameter of the first segment of the bore decreases
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abruptly, rather than tapering, to the smaller
diameter of the second bore segment.
In a further variant embodiment of the invention,
the entire center rod 68 may be constructed of a
material that is not resilient, for example a metal.
As the sheath is assembled to the syringe barrel and
the proximal end 74 of the rod is inserted through a
tapered segment of the interior bore 52, e.g., with-
in collar 34, the resilient compression of the
material of.t~e collar interior surface 54 around the
center rod proximal end 74 provides a sealing
engagement between the collar interior surface and
the center rod.
In a further variant embodiment of the invention,
the tapered segment of the collar interior surface is
replaced by a necked down portion of the interior
bore where the bore diameter changes abruptly from
the first diameter to the second diameter at an
annular wall that is perpendicular to the bore center
axis. This embodiment is illustrated in dashed lines
in Figures 4. In this embodiment the tapered rod end
74 engages against the inner peripheral edge of the
annular wall, thus producing a seal within the bore.
In all of the embodiments of the invention de-
scribed above, with the sheath 16 removably attached
to the syringe barrel 14 and the center rod 68
extending through the interior bore 52, the bore is
sealed from the barrel interior chamber 36 preventing
any substance 76 contained within the chamber from
potentially blocking the interior bore 52.
