The invention relates to a pre-filled disposable syringe to be
used in the administration of powdered drug diluted at the time
of injection. The novelty resides in that the plunger head, along
with an elastomer head, constitute a particular valve acting as
a function of plunger displacements.
1. A disposable syringe comprising;
an elongated housing means defining a chamber;
a plunger means reciprocally mounted in said housing, said plunger
means having a plunger portion, an active head portion and a short
portion connecting said plunger portion to said active head portion;
head means sealingly mounted within said chamber for dividing said
chamber into a first variable volume chamber and a second variable
volume chamber having an outlet means, said head means defining
(1) an inner cavity for receiving said active head portion for reciprocal
movement of said active head portion within said inner cavity, (2)
a first conduit about said short portion for communicating said
first variable volume chamber with said inner cavity, and (3) a
second conduit for communicating said inner cavity with said second
variable volume chamber; and
means for reciprocating said plunger means in said housing in (1)
a first direction for increasing the volume of the second variable
volume chamber wherein a fluid in the first variable volume chamber
is communicated from the first variable volume chamber through said
first conduit, said inner cavity and said second conduit into said
second variable volume chamber, and (2) a second direction for increasing
the volume of the first variable volume chamber and decreasing the
volume of the second variable volume chamber wherein a fluid in
the second variable volume chamber communicates with the outlet
2. A syringe according to claim 1 wherein said head means comprises
an elastomeric member having a plurality of teeth means projecting
into said inner cavity for supporting said active head portion when
said plunger means is reciprocated in said first direction.
3. A syringe according to claim 2 wherein said elastomeric member
has a semi-spherical cavity which communicates said first variable
volume chamber with said first conduit and said plunger has a corresponding
semi-spherical portion which seats in said semi-spherical portion
of said elastomeric member when said plunger means is reciprocated
in said direction for sealing communication between the first variable
volume chamber and said second variable volume chamber.
4. A syringe according to claim 3 wherein said active head portion
has a projection extending from a body portion for sealing said
second conduit wherein said plunger means is reciprocated in said
5. A syringe according to claim 4 wherein the body portion seals
in an inner surface of the elastomeric member defining the inner
cavity where said plunger means is reciprocated in said second direction.
I. FIELD OF THE INVENTION--PRIOR ART
The instant invention relates to a disposable syringe with two
variable volume chambers for administering liquid products or diluted
powdered drugs. These syringes are of the type commercialized with
the product already contained therein. They are also suitable for
including, separately, powdered drug and a diluent, which are mixed
at the time of injection. Therefore, they are included in the group
usually called pre-filled syringes, since they are already provided
with the medicine, thus assuring no contact of the user with the
More particularly, the instant invention relates to a syringe of
the above mentioned type comprised by a main cylindrical, hollow
body, containing the medicine to be administered, and through which
a coaxial plunger is located. In all cases the lower base of said
main cylindrical body has an opening through which the rear end
of said coaxial plunger projects, and has an annular flange in order
that the user may push or pull manually the plunger. Further, at
the opposite base of said main body, there is a hollow, coaxial
and generally frusto-conical nozzle, constituting the plugging means
for coupling and fixing the injection needle, which is housed inside
a protecting sheath removably coupled to said upper base of the
Several syringes like that defined above are already known. Most
of them are syringes having a single tight chamber wherein the pharmaceutical
product is housed; in this case, the plunger active head is located
at the lower open base of the main body, displacing towards the
opposite base, propelling the contents to the outlet nozzle wherein
the injection needle is connected. The disadvantage of these syringes
is that they are not suitable for containing powdered drugs since
they have no resource for separating the drug from the diluent before
injection, nor the means required for producing the mixture during
Some kinds of pre-filled double chamber disposable syringes are
also known. These are used for the cases in which the powdered drug
is housed into one chamber and the diluent into the other chamber;
simultaneous dilution and administration of the medicine being attained
by the plunger displacement. In these cases, within said main body,
there are two adjacent tight chambers, separated by valves which,
through said plunger displacement, allow communication between chambers,
thus mixing and diluting the drug.
Among double chamber syringes, that disclosed in Argentine patent
No. 247101 also filed in the U.S., is particularly incorporated
as a reference.
Although results with the mentioned types of syringes are satisfactory,
their construction is delicate, requires high precision and their
cost is relatively high for disposable syringes.
A new pre-filled disposable syringe has been developed by the owner
of the cited patent. This syringe may contain the powdered product
and the diluent, duly separated, at the same time being a single
chamber syringe. That is, the assembly may act as any conventional
liquid product syringe or may be pre-filled with powdered drug and
diluent, without modification thereof. In this case, the lower base
of the main body is tightly closed by an elastomer plug including
a conduit through which the plunger rod passes; the active head
of said plunger being also an elastomer plug solidary to said rod,
its peripheral edge bearing on the inner cylindrical surface of
the main body and including to this end a flexible annular flange
allowing liquid passage upwardly when the plunger descends; while
during the upward stroke of the plunger, said peripheral annular
flange causes the tight closure and displaces the product towards
the nozzle connected to the injection needle.
The embodiment mentioned above constitutes an improvement over
syringes with intermediate valve means due to economical reasons.
Nevertheless, the use of the flexible annular flange at the peripheral
edge of the plunger head rather impairs tightness when liquid displaces
towards the injection needle; also, liquid passage is not always
assured when the plunger displaces in the reverse direction propelling
liquid from the lower chamber to the upper chamber.
II. NOVELTY OF THE INVENTION
The syringe of the instant invention may act as pre-filled disposable
syringe for powdered drugs and diluent, using a plunger having an
elastomer active head acting as an intermediate partition.
In this case, the interior of the main body is also divided into
two variable volume chambers; an upper chamber wherein the powdered
drug is contained and a lower chamber housing the diluent.
When the plunger displaces in a direction opposite to that used
for injection, the elastomer active head allows liquid passage towards
the upper chamber, containing the powdered drug, thus attaining
mixture and dilution thereof.
When such plunger displaces towards the nozzle connecting to the
needle, i.e., during injection, the diluted product is easily administered
to the patient.
The novel feature of the instant invention resides in that the
active plunger head acts in combination with an elastomer head enclosing
it, constituting in turn the tight closure separating adjacent variable
volume chambers. The tight closure is produced by the peripheral
edge of the elastomer head on the inner cylindrical surface of the
main body. Passage of diluent to the upper part housing the powdered
drug is produced through the central region of said elastomer head.
The central region of said elastomer head has a particular shape,
cooperating with the plunger active head, producing a valve opening
when the plunger descends towards the lower base of the main body;
while a valve closure is attained when the plunger ascends towards
the outlet nozzle to the injection needle.
III. BRIEF DESCRIPTION OF THE DRAWINGS
A preferred, non-limiting, embodiment of the invention will be
hereinbelow described in connection with the accompanying drawings,
The first sheet of drawings shows the invention when used for administering
pre-filled liquid products with a disposable syringe.
FIG. 1 is a longitudinal cross section of a disposable syringe
showing the plunger of the invention.
FIG. 2 is a longitudinal section with the plunger at the intermediate
FIG. 3 is a longitudinal section, with the same plunger at a lower
position and the injection chamber defined at its maximum capacity.
FIG. 4 is another longitudinal section, showing the action and
arrangement of the valve means when injection is initiated.
The second sheet of drawings shows the invention when used for
administering powdered drug diluted at the time of injection.
FIG. 5 is a longitudinal section showing the same syringe, with
the products separated into adjacent chambers.
FIG. 6 is a longitudinal section showing mixing of the pre-filled
FIG. 7 is a longitudinal section showing schematically the operation
of the assembly upon injection.
In all figures, the same reference numerals designate the same
or equivalent elements.
IV. DETAILED DESCRIPTION OF THE INVENTION
As shown by the drawings, the disposable syringe of the instant
invention is comprised by a main body 1 which is a straight axis
circular cylinder; the lower base 2 is open and includes the conventional
cantilever annular flange 3 employed by the user for operating the
plunger. The substantially conical upper base 4 has the coaxial
injection nozzle 5 which, along with the annular flange 6 defines
the coupling for the plugging cone of the injection needle. Plunger
7 displaces through the interior, coaxial to said nozzle 5 which
has the conventional rod projecting outwardly passing through plug
9 and ending at the broadening 10 required for manual operation
As shown by the drawings, plug 9 closing the lower opening 2 acts
as a closure stop for the variable volume chamber 11. It is an elastomer
plug having a central conduit 12 through which plunger 7 displaces
with enough fitness for preventing liquid leakage from chamber 11.
Such plug bears against the cylindrical wall of the main body and
extends towards the sides for locking at said flange 3 of body 1.
Such closure may be further obtained using special adhesives or
pressure metal covers such as those shown by reference 13 in FIGS.
5 6 and 7.
As shown by the drawings, the plug 9 has an annular cavity 14 located
at the inner face surrounding said conduit 12; this produces an
overlapping coupling when head 15 enclosing the plunger head is
at its maximum lower point.
The novelty of the invention resides in the valve means defined
by the active head 17 of the plunger and the elastomer head 15 enclosing
it. In fact, said plunger 7 defines, adjacent its upper end, a cap-shaped
seating edge 18 facing a lower cavity 19 of the elastomer head.
Then, the plunger defines a short portion 20 narrower and longer
than conduit 19 of said elastomer head. Finally, the end of the
plunger constitutes its active head 17 housed into a valve inner
cavity 22 defined at said elastomer head 15.
The apex 8 of elastomer head 15 is open, while the lower base of
cavity 22 has teeth 21 constituting the bearing means for the plunger
As shown in the figures, the frusto-conical shape of the active
head 17 along with the shape of the apex portion 8 determine a
particular valve opening and closure means allowing passage of the
contents through the variable volume chambers 11 and 16.
In fact, FIG. 1 shows the syringe containing the liquid product
to be administered, as marketed, i.e., with the head 15 acting as
upper closure plug.
FIG. 2 shows the way in which the user should displace the plunger
to obtain passage of the contents from the lower chamber 11 to the
upper chamber 16. The position adopted by the active head 17 allows
passage of liquid through the inner cavity 22 and projection through
the opening of apex 8.
FIG. 3 shows the maximum outward expansion of plunger 7; herein,
the elastomer head bears on the lower plug 9 the syringe being
in condition of initiating the usual injection action.
FIG. 4 shows that, during the ascending stroke of plunger 7 the
cap-shaped end thereof 18 produces valve closure on the lower seating
cavity 19. Simultaneously, the frusto-conical surface of the active
head 17 seats on the inner wall of the elastomer head 15 at the
region adjacent its apex 8. In this way, liquid leakages are prevented
It is to be noted that other alternatives for the cooperating valve
closure carried out by the elastomer head 15 and the active head
17 are also possible within the scope of the invention.
FIGS. 5 6 and 7 show operation of the assembly (without any modification)
when acting as pre-filled syringe containing powdered drug and diluent.
Solid material, at the upper region, designated with reference
M, is separated from the diluent contained into chamber 11. Prior
to injection, the user should shift the plunger 7 in the direction
shown by FIG. 6; in this way, diluent passes to the upper chamber
16 and the mixture is produced.
Finally, FIG. 7 shows the double valve closure obtained when the
plunger 7 during injection, displaces the mixture towards the outlet