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 What is claimed is:
1. A disposable syringe comprising: a syringe body hollow on an
inside and open at a front end and at a rear end thereof; 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 a rear
thereof with a manually drivable stem driven out of the syringe
body though the rear end thereof, and an injection needle integral
with a needle-carrier that can be engaged to the front 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 an 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 and retraction of
the needle into the syringe body, said stem extending through the
spring means; 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 protection 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
protection.
2. The syringe of claim 1 wherein said retaining tongues have
an inwardly tapered surface at their end, terminating in said second
spring-bearing projection.
3. The syringe of claim 1 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.
4. 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.
5. 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.
6. The syringe of claim 1 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 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.
8. The syringe of claim 7 wherein the outer surface of said annular
projection is tapered to cooperate with the inner tapered surface
of said retaining tongues.
9. 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.
10. The syringe of claim 9 wherein at the rear end of said needle-carrier
are flexible members 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 members inward and engage
the grooves of said members.
11. 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.
12. The syringe of claim 11 wherein at the rear end of said needle-carrier
are flexible members 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 members inward and engage
the grooves of said members.
13. 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.
14. The syringe of claim 1 wherein said needle-carrier is mounted
integrally on the plunger.
15. The syringe of claim 14 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
The present invention refers to an improved disposable syringe.
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.
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.
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.
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.
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.
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.
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.
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.
Another object of the present invention is to provide such a disposable
syringe which is able to prevent further attempts at use.
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.
These objects are achieved according to the invention with the
characterstics listed in appended independent claim 1.
Advantageous embodiments of the invention are apparent from the
dependent claims.
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.
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.
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.
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.
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.
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:
FIG. 1 is a part-sectional exploded view illustrating the disposable
syringe according to the invention;
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;
FIG. 3 is a broken-away part-sectional view illustrating the syringe
of FIG. 1 assembled with the plunger in the retracted position;
FIG. 4 is a cross-sectional view of the stem of the plunger taken
along the plane IV--IV of FIG. 1;
FIG. 5 is a cross sectional view of a sleeve member taken along
the plane V--V of FIG. 1.
The disposable syringe according to the invention is described
with the aid of the figures.
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.
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.
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.
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 members 13 separated from
each other by an axial slot 14 are connected to the cylindrical
block 12. Each flexible member 13 has an outward facing groove 15.
The needle-carrier 11 is inserted in the hole of the head 2 and
the grooves 15 of the member 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.
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 23 ends in a tooth 24
having a tapered part 27 protruding inward, which ends with a radial
abutment surface 25.
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.
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.
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.
A plunger 40 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.
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.
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.
Operation of the syringe according to the invention is described
hereunder.
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 members 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.
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.
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.
As shown in FIG. 2 when the plunger 40 reaches the end of its
stroke, the members 13 of the needle-carrier 11 enter the tapered
cavity 54 of the head 51 of the stem 50.
Consequently the members 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.
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.
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.
Moreover, according to per se known solutions which therefore are
not illustrated, the grooves 15 of the members 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.
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.
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.
a non-safety solution can also be provided in which the needle
remains permanently mounted on the head of the syringe body.
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. |