Abstrict A disposable syringe comprises a syringe body (1), a plunger (40)
mounted on a stem (50) slidable inside the syringe body (1), and
an injection needle (10) integral with a needle-carrier (11) engageable
with the fore end (2) of the syringe body (1) or the plunger, retaining
means (20 23 24) able to retain spring means (30) under compression
being provided integrally with the syringe body (1) and engagement
means (59) able to cooperate with the retaining means (23) to release
the spring means (30), when the plunger (40) has reached the end
of its stroke, being provided integrally with said stem (50), so
that the spring means (30) can act on the stem (50) to cause retraction
thereof into the retracted position.
Claims 1. A disposable syringe comprising: a syringe body hollow on the
inside and open at the front and at the rear; a plunger which is
slidable inside the syringe body having an injection stroke extending
from a retracted syringe filling position to an advanced syringe
emptying position, said plunger being provided at the rear with
a manually drivable stem driven out of the syringe body through
the rear end thereof, and an injection needle integral with a needle-carrier
that can be engaged to the fore end of the syringe body or the plunger,
wherein associated with said syringe body, retaining means able
to retain spring means under compression are provided and, integrally
with said stem, engagement means able to cooperate with said retaining
means to free said spring means, when said plunger has reached the
end of the injection stroke, are provided, so that said spring means
can act on said stem to cause retraction thereof into the retracted
position.
2. The syringe of claim 1 wherein said retaining means comprise
flexible retaining tongues protruding axially form the rear end
of the syringe body and said spring means are interposed between
a first spring-bearing wall protruding radially from the inner surface
of the syringe body and a second spring-bearing projection or surface
protruding radially from the inner surface of said retaining tongues,
said engagement means causing outward bending of said retaining
tongues so as to free one end of said spring means retained by said
second spring-bearing projection.
3. The syringe of claim 2 wherein said retaining tongues have
an inwardly tapered surface at their end, terminating in said second
spring-bearing projection.
4. The syringe of claim 2 wherein said retaining means comprise
a cylindrical sleeve hollow on the inside and open at its ends,
able to be inserted in the rear end of said syringe body, said first
spring-bearing projection being obtained from the bottom wall of
the sleeve, said retaining tongues being obtained by means of a
plurality of axial notches in the sleeve open at the opposite end
to the bottom wall, said bottom wall having a hole able to allow
the passage of said stem.
5. The syringe of claim 4 wherein said syringe body has an abutment
projection which protrudes radially from its inner surface, to lock
said sleeve, in such a position that the end of the tongues protrudes
outward from the rear end of the syringe body.
6. The syringe of claim 2 wherein said engagement means comprise
a plate disposed at the rear end of said stem, said plate having
an annular projection which protrudes axially and forward therefrom
around said stem, said annular projection being able to cooperate
with said retaining tongues to cause outward bending thereof.
7. The syringe of claim 4 wherein said engagement means comprise
a plate disposed at the rear end of said stem, said plate having
an annular projection which protrudes axially and forward therefrom
around said stem, said annular projection being able to cooperate
with said retaining tongues to cause outward bending thereof.
8. The syringe of claim 6 wherein between the inner surface of
said annular projection and the outer surface of the rear end of
the stem a gap is left, such as to allow the passage of said spring
means so that the end of said spring means, when it is freed from
said second spring-bearing projection, can abut against the inside
surface of said end plate of the stem and the action of the spring
means can cause retraction of the stem.
9. The syringe of claim 8 wherein the outer surface of said annular
projection is tapered to cooperate with the inner tapered surface
of said retaining tongues.
10. The syringe of claim 1 wherein said needle-carrier is mounted
inside the head of the syringe body with its rear end inside the
chamber of the syringe body, the plunger having a through hole which
receives the head of said stem, the head of the stem having a blind
hole with engagement means able to engage with the rear end of said
needle-carrier so as to retain it to allow the needle to be pulled
inside the chamber of the syringe body, during retraction of said
stem.
11. The syringe of claim 2 wherein said needle-carrier is mounted
inside the head of the syringe body with its rear end inside the
chamber of the syringe body, the plunger having a through hole which
receives the head of said stem, the head of the stem having a blind
hole with engagement means able to engage with the rear end of said
needle-carrier so as to retain it to allow the needle to be pulled
inside the chamber of the syringe body, during retraction of said
stem.
12. The syringe of claim 10 wherein at the rear end of said needle-carrier
are flexible tongues with grooves able to engage in a first collar
provided in the inner surface of the head of the syringe body and
said engagement means are a collar provided on the blind hole of
the fore end of the stem, able to bend said tongues inward and engage
the grooves of said tongues.
13. The syringe of claim 11 wherein at the rear end of said needle-carrier
are flexible tongues with grooves able to engage in a first collar
provided in the inner surface of the head of the syringe body and
said engagement means are a collar provided on the blind hole of
the fore end of the stem, able to bend said tongues inward and engage
the grooves of said tongues.
14. The syringe of claim 12 wherein said grooves have different
profiles so that the needle-carrier is retained by the collar in
a bent position with respect to the axis of the syringe body.
15. The syringe of claim 1 wherein said needle-carrier is mounted
integrally on the plunger.
16. The syringe of claim 15 wherein sealing means are provided
in said head of the syringe body to prevent leakage of liquid from
the gap formed between the outer surface of the needle and the inner
surface of the head and in that in said needle-carrier or in said
plunger at least one channel is provided to put the inner passageway
of the needle in communication with the chamber of the cylindrical
body.
Description DESCRIPTION
[0001] The present invention refers to an improved disposable syringe.
[0002] As is known, a syringe generally comprises a cylindrical
body open at the rear to receive a plunger. An internally hollow
needle is mounted at the head of the syringe body. The liquid contained
in a vial is drawn into the syringe body through the needle by retracting
the plunger. The liquid contained in the syringe body is injected
into the patient's body through the needle by pressing on the plunger.
[0003] Because of health regulations and to avoid transmission
of infectious diseases, syringes must generally be used only once
and then discarded. For this reason there is a growing demand on
the market for disposable syringes able to prevent re-use.
[0004] Moreover, syringes generally have drawbacks from a safety
viewpoint. In fact, once the syringe has been used, the needle remains
exposed at the head of the syringe body, with the risk of injury
and accidental stabs.
[0005] This drawback is overcome in part by European patent EP
0636381 which describes a guard device for syringe needles. In this
case, when the plunger of the syringe reaches the end of its stroke,
the front end of the plunger stem captures the needle. Once the
injection is completed, the user must manually retract the stem;
in this manner the needle is pulled inside the syringe body by the
head of the stem into the safety position which prevents accidental
stabs.
[0006] This solution presents the drawback that the user, having
finished the injection, can forget to carry out retraction of the
stem, leaving the needle exposed and thus rendering the protection
device ineffective.
[0007] Patent application PCT WO 99/37345 by the same applicant
as the present application describes a disposable safety syringe
which has a needle-covering sleeve mounted axially on the syringe
body and slidable from a retracted position, in which it leaves
the needle exposed to allow injection, to an advanced position in
which it completely covers the needle, preventing re-use of the
syringe and acting as a guard against accidental stabs.
[0008] Once the injection has been carried out, the sleeve is automatically
brought into the extracted safety position, by means of an automatic
mechanism and without any intervention by the user. Nevertheless,
this solution has a certain complexity due to the provision and
movement of the needle-covering sleeve.
[0009] The object of the present invention is to eliminate the
drawbacks of the prior art providing an improved disposable syringe
that is practical, versatile, economical and simple to make.
[0010] Another object of the present invention is to provide such
a disposable syringe which is able to prevent further attempts at
use.
[0011] Another object of the present invention is to provide such
a disposable syringe that is extremely safe and able to prevent
accidental wounds after use thereof.
[0012] These objects are achieved according to the invention with
the characterstics listed in appended independent claim 1.
[0013] Advantageous embodiments of the invention are apparent from
the dependent claims.
[0014] The disposable syringe according to the invention comprises
a syringe body hollow on the inside and open at the front and rear,
a plunger slidable inside the syringe body with an injection stroke
extending from a withdrawn or retracted syringe-filling position
to an advanced syringe-emptying position, and an injection needle
integral with a needle-carrier that can be engaged to the front
end of the syringe body or the plunger. The plunger is provided
at the rear with a manually drivable stem driven out of the syringe
body through the rear end thereof.
[0015] The peculiarity of the disposable syringe according to the
invention is represented by the fact that, associated with said
syringe body, retaining means are provided to retain spring means
under compression and, integrally with said stem, engagement means
are provided to cooperate with said retaining means to free said
spring means when said plunger reaches the end of the injection
stroke. In this manner, when the plunger reaches the end of the
injection stroke, the spring means are automatically released from
the retaining means and act on an abutment surface of the stem causing
retraction thereof into the retracted position.
[0016] An advantageous embodiment of the invention for safety purposes,
provides for the use of a needle-carrier mounted on the inside of
the fore end of the syringe body and a stem which has a fore end
with means able to couple with the rear end of the needle-carrier
in order to retain it. In this manner, when the spring means cause
retraction of the stem, the needle-carrier draws the needle with
it into the syringe body chamber.
[0017] A further advantageous embodiment of the invention for safety
purposes provides for use of a needle-carrier mounted integrally
with the plunger. In this case the head of the syringe body provides
sealing means to prevent leakage of the liquid from the annular
gap formed between the outer surface of the needle and the inner
surface of the cylindrical body. Moreover, at least one channel
that puts the inner bore of the needle in contact with the chamber
of the cylindrical body will be provided in the needle-carrier or
in the plunger.
[0018] The advantages of the disposable syringe according to the
invention are obvious. In fact said syringe, by causing automatic
retraction of the stem of the plunger, once the injection is completed,
prevents re-use thereof. Moreover, in the case of the needle-carrier
being engageable with the plunger, re-entry of the plunger at the
same time draws the needle into the chamber of the syringe body,
avoiding accidental stabs with the utmost safety.
[0019] Further characteristics of the invention, will be made clearer
by the detailed description that follows, referring to a purely
exemplary and therefore non-limiting embodiment thereof, illustrated
in the appended drawings, in which:
[0020] FIG. 1 is a part-sectional exploded view illustrating the
disposable syringe according to the invention;
[0021] FIG. 2 is a view partially in axial section and partially
broken off, illustrating the disposable syringe of FIG. 1 assembled
with the plunger in the advanced position;
[0022] FIG. 3 is a broken-away part-sectional view illustrating
the syringe of FIG. 1 assembled with the plunger in the retracted
position;
[0023] FIG. 4 is a cross-sectional view of the stem of the plunger
taken along the plane IV-IV of FIG. 1;
[0024] FIG. 5 is a cross sectional view of a sleeve member taken
along the plane V-V of FIG. 1.
[0025] The disposable syringe according to the invention is described
with the aid of the figures.
[0026] The syringe comprises a cylindrical body 1 hollow on the
inside, defining a cylindrical chamber. The rear end of the body
1 is open toward the outside and has a flange 3 that protrudes radially
outward.
[0027] At a short distance from the rear end of the body 1 in
the inner surface of the body 1 a projection 4 is provided defining
an abutment surface that protrudes radially inward.
[0028] The fore end of the body 1 is tapered and ends with a head
2 open toward the outside, in the form of a cylindrical tang, with
a smaller diameter than that of the body 1. In the inner surface
of the head 2 a collar 5 is provided that protrudes radially inward.
[0029] A needle 10 is carried by a needle-carrier 11. The needle-carrier
11 comprises a cylindrical block 12 that has an axial hole to receive
an end of the needle 10. Two flexible tongues 13 separated from
each other by an axial slot 14 are connected to the cylindrical
block 12. Each flexible tongue 13 has an outward facing groove 15.
[0030] The needle-carrier 11 is inserted in the hole of the head
2 and the grooves 15 of the tongues 13 engage in the collar 5 of
the head 2 so as to retain the needle-carrier. In order to prevent
the needle 10 from being extracted, a retaining cap 16 having a
frustoconical shape is mounted on the head 2. The cap 16 engages
the head 2 the part of cylindrical block 12 that protrudes outward
from the head, and a small portion of needle 10 near the cylindrical
block 12.
[0031] A cylindrical sleeve 20 hollow on the inside, having an
outside diameter equal to or slightly smaller than the inside diameter
of the cylindrical body 1 has a bottom or end wall 21 in which
a large circular hole 22 is formed, so that the bottom wall 21 forms
an annular inward-facing projection. As shown in FIG. 5 at the
opposite end to the bottom wall 21 the sleeve 20 has four flexible
tongues 23 each defined by two longitudinal slots 26 so as to
be able to bend inwardly and outwardly. Each tongue 13 ends in a
tooth 24 having a tapered part 27 protruding inward, which ends
with a radial abutment surface 25.
[0032] By outwardly parting the tongues 23 a coil spring 30 is
inserted axially into the sleeve 20. The spring 30 is kept under
compression with its ends abutting respectively against the bottom
wall 21 and against the abutment surface 25 of the tooth 24.
[0033] The sleeve 20 is inserted from the rear opening of the syringe
body 1 until its bottom wall 21 abuts against the projection 4
of the syringe body. In this position an end part of the tongues
23 protrudes axially out of the syringe body 1.
[0034] For simplicity of construction a sleeve 20 has been illustrated
separate from the syringe body 1. However, the sleeve 20 can be
formed in a single body with the syringe body 1. That is to say,
the flexible tongues 23 can be formed at the rear end of the syringe
body 1 and the spring 30 is interposed between an abutment surface
of the syringe body and the abutment surface 25 of the teeth 24
of the tongues 23.
[0035] A plunger 30 is made of plastic material and has such a
shape as to be able to slide tightly inside the chamber of the syringe
body 1. The plunger 40 has a cavity 41 able to receive in engagement
a head 51 of a stem or piston 50.
[0036] The head 51 of the stem 50 has a first annular flange 52
which engages in an annular seat 42 of the cavity 41 and a second
abutment flange 53 against which the base of the plunger 40 abuts.
At the end of the head 51 of the stem 50 is a blind tapered aperture
54 delimited at its open end by a collar 55 which protrudes inward.
[0037] As shown in FIG. 4 the stem 50 has an axial cylindrical
part 56 from which four ribs 57 depart radially and extend substantially
for the entire length of the stem 50. The rear end of the stem 50
has a circular flange 58 disposed transversally, with an annular
protruding part 59 which provides a tapered outer lateral surface
60 and a straight inner lateral surface 61 defining a gap 62 with
the end of the ribs 57 of the stem 50.
[0038] Operation of the syringe according to the invention is described
hereunder.
[0039] In an initial situation the needle 10 is mounted on the
head 2 of the syringe body 1 with the collar 5 of the head of the
syringe body engaged in the grooves 15 of the tongues 13 of the
needle-carrier 11. The sleeve 20 is mounted in the syringe body,
with the teeth 24 of the tongues protruding from the rear end of
the syringe body. The plunger 40 is situated inside the chamber
of the syringe body, mounted on the head of the stem 50.
[0040] Initially the needle is positioned in the liquid to be drawn,
and the user retracts the stem 50. The consequent retraction of
the plunger 40 causes a depression in the chamber of the syringe
body 1 thus the liquid is drawn into the chamber of the syringe
body 1 through the needle 10.
[0041] When the injection is carried out, the user applies pressure
to the flange 58 of the stem 50 causing an advancement of the plunger
40 which thus pushes the liquid which is injected through the needle
10.
[0042] As shown in FIG. 2 when the plunger 40 reaches the end
of its stroke, the tongues 13 of the needle-carrier 11 enter the
tapered cavity 54 of the head 51 of the stem 50.
[0043] Consequently the tongues 13 undergo an inward bending, and
their grooves 15 disengage from the collar 5 of the head of the
syringe body. At the same time, the grooves 15 engage in the collar
55 of the end of the head 50 of the stem. In this manner the head
of the stem retains the needle-carrier 11.
[0044] When the plunger 40 is at the end of its stroke, the tapered
surface 60 of the protruding annular part 59 of the end flange 58
of the stem begins to encounter the tapered surface 27 of the teeth
24 of the tongues 23 of the sleeve 20. Consequently the tongues
23 of the sleeve bend outward, thus the abutment surface 25 of the
teeth 24 no longer retain the end of the spring 30 which is released,
passing through the gaps 62 between the stem 50 and the protruding
part 59 of the end flange 58 and abuts against the end flange 58
pushing it in the direction of retraction of the stem 50.
[0045] As shown in FIG. 3 since the needle-carrier 11 is constrained
to the head 51 of the stem 50 when the spring 30 causes retraction
of the stem, the needle 10 is drawn by the needle-carrier into the
chamber of the syringe body 1. In this manner the syringe cannot
be used for a further injection and does not allow accidental stabs,
since the needle remains protected inside the chamber of the syringe
body.
[0046] Moreover, according to per se known solutions which therefore
are not illustrated, the grooves 15 of the tongues 13 of the needle-carrier
can have profiles with a different shape to allow bending of the
needle-carrier with respect to the axis of the syringe body. In
this manner the needle 10 is no longer in axis with the syringe
body and cannot accidentally protrude through the hole in the head
2 of the syringe body.
[0047] The present embodiment of the invention has been described
with reference to a solution in which the needle-carrier is mounted
inside the head of the syringe body so as to be captured by the
plunger.
[0048] However, other solutions can be provided, such as for example
the use of a needle-carrier mounted integrally with the plunger.
In this case the head of the syringe body has sealing means to prevent
leakage of the liquid from the annular gap formed between the outer
surface of the needle and the inner surface of the head of the cylindrical
body. Moreover, at least one channel which places the inner passageway
of the needle in communication with the chamber of the syringe body
will be provided in the needle-carrier or in the plunger.
[0049] A non-safety solution can also be provided in which the
needle remains permanently mounted on the head of the syringe body.
[0050] Numerous variations and changes of detail within the reach
of a person skilled in the art can be made to the present embodiment
of the invention without thereby departing from the scope of the
invention, set forth in the appended claims.
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