Note: Descriptions are shown in the official language in which they were submitted.
TITLE OF THE INVENTION 13~
Self-block;ng hypoderm;c syr;nge for once-only use,
compr;sing a needle protection cap.
BACKGROUND OF THE INVENTION
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This invention relates to a self-blocking hypodermic
lC syringe for once-only use, which cannot be reused after it
has been once used, and is provided with a needle protection
- cap which is automatically transferred into its protection
position after use.
In medical practice, medicaments are frequently
administered to the patient hypodermically by means of a
needle and syringe.
In order to ensure maximum protection from infection
and the like, sterile syringes for once-only use are usually
employed, these being packaged in sealed containers to be
opened at the moment of use.
However, syringes are also used by drug addicts for
drug injection, and with this category of person a
considerable increase has been noted in the spread of viral
illnesses, such as type B hepatitis and acquired immuno-
deficiency syndrome (AIDS), the cause of which is thecontagion transmitted by the use of the same syringe by more
than one person, who ignore the rule which prescribes its
once-only use.
Moreover when syringes are used to inject persons
suffering from illnesses of the aforesaid type, it can
sometimes happen that the medical functionary or whoever
carries out the injection is accidentally injured by the
used syringe needle either before fitting a protection cap
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onto the ne~dle or while fitting it, or before placing the
syringe ;n a closed conta;ner for its d;sposal, with the
danger of contracting the infecti on .
Finally, syringes used by drug addicts for drug taking
are very often carelessly thrown away in public places such
as public gardens after use, so exposing park attendants and
other persons, especially children, to the danger o~
accidental pricking and possible infection.
Certain syringes comprise means for controlling the
plunger stroke within the cylindrical body for various
reasons.
For example, GB-A-551 545 discloses a syringe
comprising means for delaying or braking the plunger stroke
within the cylindrical body and for enabling the user to
determine the quantity of injected liquid by feel.
DE-A-3 107 414 discloses blocking means for preventing
the extraction of a plunger from the cylindrical body in
order to avoid contaminating the space which is to contain
the liquid to be injected, and US-A-l 434 381 discloses a
syringe provided with elastic braking or delay means to
prevent accidental introduction of air into the liquid
contained in the syringe or accidental leakage of this
liquid, or again accidental escape of the plunger from the
cylindrical body.
However, none of the known syringes comprises means
for preventing the re-use of a once-only usable syringe or
for preventing accidental pricking after the syringe has
been used.
The problem therefore arises of preventing the spread
of contagion by making it impossible to use the same syringe
more than once, independently of the desire or negligence of
the user, and of isolating the needle after the syringe has
been used so that the needle is made safe.
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SUMMARY OF THE INVENTION
These results are attained according to the present
invention by a self-blocking hypodermic syringe for
once-only use comprising a cylindrical body which at its
front end carries means for connection to a hypodermic
needle and is open at its opposite end and contains a
plunger which slides in a fluid-tight manner and is provided
with a gripping rod, characterised by also comprising
elastic means for blocking the plunger intake stroke which
are initially located in an inactive position and are
transferred into an active position during the first syringe
intake and injection operation, when in said active position
the elastic means being disposed in a position secured to
the cylindrical body of the syringe and interfering with the
plunger intake stroke.
According to a currently preferred embodiment, the
means for blocking the plunger intake stroke consist of a
split-ring which before the syringe is initially used
embraces the minor diameter region of a frusto-conical
portion of the rod, which converges in the direction in
which the plunger is driven for injection. The minor
diameter region of said frusto-conical portion has a
diameter less than the rod diameter and the major diameter
region has a diameter substantially equal to or slightly
less than the inner diameter of the cylindrical body. The
syringe cylindrical body comprises an annular bulge which is
able to receive the split-ring when this is drawn in front
of it during the initial liquid intake stage, said bulge
having an inner diameter greater than the diameter of the
major diameter region of the frusto-conical portion plus the
thickness of the split-ring and being positioned at a
distance from that end of the cylindrical body carrying the
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needle which exceeds the distance between the front end of
the plunger and the rear surface of its frusto-conical
portion. When in its undeformed state, the split-ring has an
inner diameter less than the maximum diameter of the
frusto-conical portion and an outer diameter greater than
the inner diameter of the cylindrical body, and is
elastically deformable to widen-out into the bulge under the
action of the frusto-conical surfase as the plunger is
driven in.
Before the syringe is initially used, the split-rina
is in a position forward of the bulge in the cylindrical
body, and is in its elastically deformed contracted state.
The distance between the split-ring when in its
initial position, i.e. embracing the minor diameter region
of the frusto-conical portion, and the bulge in the
cylindrical body is less than the stroke of the plunger
which corresponds to the minimum scheduled liquid dosage for
which the syringe can be used.
According to a further characteristic, the syringe of
the invention also comprises a slidable cap coaxial to the
syringe body and covering the body itself, and being
provided at its front with an exit hole for the needle and
further having members for its fastening to the syringe
body, and elastic thrust means, said cap when in its
retracted position leaving the needle exposed and when in
its advanced position covering the needle, the fastening
members being moved into their release position by release
means associated with the first forward movement of the
plunger.
Specifically, the cap fastening members consist of
elastic tongues provided in the rear part of the cap and
having their ends turned inwards to form a hook so that when
the cap is in its retracted position they become inserted
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into corresponding slots in the syringe body to axially lock
the cap, the release means consisting of an elastic element
which is provided within the syringe in a position
corresponding to the slots in the syringe body which house
S the hook-shaped ends of the cap tongues and is arranged to
be radially deformed by the forward stroke of the plunger
during the first injection, so urging the hook-shaped ends
out of the relative slots.
The syringe body also possesses one or more recesses
for receiving the cap tongue fastening elements when the cap
is in its advanced position in which it encloses the needle,
to thus blocking any further sliding of the cap and prevent
its escape.
The elastic element inside the syringe, which urges
the hook-shaped ends out of the relative slots, consists of
the split-ring which before the syringe is used embraces the
minor diameter region of the forwarding converging
frusto-conical portion of the plunger, and is arranged to be
dragged during the intake stroke into an inner annular
cavity in the cylindrical syringe body into which the body
slots housing the hook-shaped ends of the tongues open, the
split-ring being radially deformable outwards under the
action of the frusto-conical portion during plunger
advancement.
The elastic means for urging the cap into its advanced
position consis~ of a spiral spring interposed between the
front surface of the syringe body and the front end of the
plunger, said elastic means being preloaded by the cap being
placed in its retracted position, before the syringe is
used.
Under the initial conditions, before the syringe is
used, the front end of the cap is rearward of the base of
the needle by a distance equal to the distance through which
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the cap has to be advanced in order to completely release
the hook-shaped ends of the cap tonglles from the respective
slots in the syringe body without their re-insertion into
the slots being possible.
The hook-shaped ends of the cap tongues have their
outer surface bevelled towards the rear of the syringe, and
in correspondence with these the recesses in the syringe
body which receive the cap tongue fastening elements when
the cap is in its advanced position have an undercut rear
wall to cause the tongues to deflect inwards should the cap
receive a rearward thrust.
According to a particular embodiment, the needle can
have its axis oblique to the axis along which the cap slides
on the syringe body, and is elastically flexible during the
sliding of the cap, after completion of this sliding it
returning to its initial oblique axis position within the
cap with its free front end laterally displaced from the
axis of the front hole in the cap.
The cap is preferably constructed of transparent
material, to allow the quantity of liquid present in the
syringe body to be seen.
DESCRIPTION OF THE DRAWINGS
The invention will be more apparent from the
description of its currently preferred embodiment which is
given hereinafter by way of non-limiting example with
reference to the accompanyin~ drawings, in which:
Figure 1 is an axial section through the syringe
according to the invention ready for drawing in liquid, and
with its protection cap removed for reasons of clarity;
Figure 2 is a section on the line II-II of Figure l;
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Figure 3 shows the syringe of Figure 1 during liquid
draw-in;
Figure 4 is a section on the line IV-IV of Figure 3;
Figure 5 shows the syringe of Figure 1 during
injection;
Figure 6 is a section on the line VI-VI of Figure 5;
Figure 7 is an axial section through the syringe
according to the invention in its initial position ready for
drawing in liquid, but with its protection cap fitted;
Figure 8 shows the syringe of Figure 7 in an
intermediate stage during draw-in;
Figure 9 shows the syringe of Figure 7 when nearly at
the end of the injection stage;
Figure 10 shows the syringe of Figure 7 after use,
with the needle protected; and
Figure 11 shows an alternative embodiment of the
syringe of Figure 7 after use.
DETAILED DESCRIPTION
As shown in Figure 1, the syringe according to the
invention comprises an outer cylindrical body 1 having a
front end la shaped to connect to a needle, not shown as it
can be of known type, and a rear end lb provided with a
gripping flange. Within the cylindrical body 1 there slides
a plunger 2 provided with a seal element 3 and a rod 4
terminating with a gripping flare 5.
As best seen in Figure 3, the rod 4 carries a
frusto-conical portion 6 which converges towards the seal
element 3 and has its major diameter substantially equal to
or slightly less than the inner diameter of the cylindrical
body 1, and its minor diameter less than the diameter of the
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8 13 ~
rod 4.
A toroidal split-ring 7 which when in its rest state
has an outer diameter greater than the inner diameter of the
cylindrical body 1 and an inner diameter equal to the
diameter of the rod 4, is located about the minor diameter
region 8 of the portion 6 before initial use, and is
therefore housed within the cylindrical body 1 in the
position shown in Figure 1, in a deformed contracted state
about the minor diameter region 8 o~ the portion 6, as can
be also seen in Figure 2.
At a short distance from its rear end lb, the
cylindrical body 1 comprises an annular bulge 9 with an
inner diameter equal to the maximum diameter of the
frusto-conical portion 6 plus the width of the split-ring 7.
Under the initial conditions, as shown in Figures 1
and 2, the split-ring 7 is contracted about the minor
diameter region 8 of the frusto-conical portion 6, and the
plunger 2 is inserted completely into the cylindrical body
1, with the ring 7 in an intermediate position between the
end la of the cylindrical body 1 and the annular bulge 9.
For its use, the syringe must be filled by drawing the
medicinal liquid in by withdrawing the plunger 2 rearward.
During this stage, as shown in Figure 3, the ring 7 is
pulled by the rod 4 towards the annular bulge 9, into which
it becomes insterted by opening out elastically into its
rest state, shown in Figure 4.
The liquid intake stage can then be continued until
the syringe is filled with the required volume of medicinal
liquid, without any further movement of the ring 7 which
remains securely housed in its seat, whereas the plunger 2
can be moved to expel residual air or the like before
inserting the needle into the patient's body for injecting
the medicament.
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During the subsequent inject;on stage, the plunger 2
is driven in to expel the liquid contained in the syringe,
until the frusto-conical portion 6 comes into contact with
the split-ring 7. During advancement of the plunger 2, the
action of the surface of the portion 6 causes the ring 7 to
widen out into its dilated state shown in Figure 6, with its
inner diameter equal to the maximum diameter of the portion
6, so allowing the portion 6 to pass through as shown in
Figure 5, and enabling the plunger 2 to terminate its stroke
in order to completely expel the contained liquid.
When the frusto-conical portion 6 of the plunger 2 has
passed beyond the ring 7, this elastically assumes its rest
state, held within the bulge 9 and abutting against the flat
rear surface 6a of the frusto-conical portion 6 and thus
-
opposing any subsequent withdrawal of the plunger 2. As the
flat rear surface 6a of the frusto-conical portion 6 has a
diameter substantially equal to or slightly less than the
inner diameter of the cylindrical body 1, even if the ring 7
is forced and/or fractured it will be absolutely impossible
to withdraw the plunger 2 due to ;nterference.
This configuration therefore makes it no longer
possible to draw further liquid in, so making any second
utilisation of the syringe impossible.
The distance between the syringe front end la and the
bulge 9 and the distance between the front surface of the
seal element 3 and the surface 6a are such that the position
to which the plunger 2 has advanced when the ring 7 abuts
against the surface 6a is such as not to allow sufficient
liquid to be injected before this abutment occurs, and also
such as to allow the ring 7 to be drawn into the bulge 9
during the intake stage with even the minimum usable dosage
of medicinal liquid, so as to prevent situations occurring
in which the plunger does not become blocked after the
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initial injection, either by accident or by purposeful
manipulation.
With reference to Figure 7, the syringe according to
the invention is also provided with a cap 109 which is of
transparent material to enable the quantity of liquid
present in the syringe to be seen, and has at its front a
hole lO9a for passage of the needle lOla, the cap being
provided in its rear part with at least two elastic tongues
110 having their free ends llOa turned inwards in the manner
of a hook and inserted, when under initial conditions, in
respective slots 111 which open into the groove 108.
Between the body 1 and the front end of the cap 109
there is also provided a spring 1129 for example of spiral
type, which under initial conditions is compressed. The body
1 is also provided with an outer annular cavity 113 or
several limited cavities, disposed in correspondence with
the free ends llOa of the tongues 110.
For its use, the syringe must be filled by drawing the
medicinal liquid in by withdrawing the plunger 2 rearward.
During this stage, as shown in Figure 8, the ring 7 is
pulled by the rod 4 towards the annular groove 108, into
which it becomes inserted by opening out elastically into
its rest state, in contact with the ends llOa of the tongues
110.
The liquid intake stage can then be continued until
the syringe is filled with the required volume of medicinal
liquid, without any further movement of the ring 7 which
remains securely housed in its seat, whereas the plunger 2
can be moved to expel residual air or the like before
inserting the needle into the patient for injecting the
medicament.
During the subsequent injection stage, the plunger 2
is driven in to expel the liquid contained in the syringe,
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11
until the frusto-conical portion 6 comes into contact with
the split-ring 7. ~uring advancement of the plunger, the
action of the surface of the portion 6 causes the ring 7 to
widen out to an inner diameter equal to the maximum diameter
of the portion 6, so allowing the portion 6 to pass and
enabling the plunger 2 to terminate its stroke in order to
completely expel the liquid contained in the syringe.
During this stage the ring 7 has widened out to the
maximum diameter of the groove 108, and its outer surface
therefore acts against the ends llOa of the tongues 110 to
urge them outwards, as shown in Figure 9, so that they
deflect until they become released from the engagement with
the edge of the groove 108.
Under the action of the spring 112, the cap 109 then
advances through a distance "a" equal to the needle terminal
portion 114 which determines its maximum depth of insertion,
so that it comes into contact with the skin of the patient,
against which it remains until the injection is complete,
while the ends llOa of the tongues 110 rest against the
outer wall of the body 1 in a position forward of the groove
108, so that they are unable to re-enter the relative slots
1 1 1 .
When the frusto-conical portion 6 of the plunger 2 has
passed beyond the ring 7, it elastically assumes its rest
state, held within the groove 108 and abutting against the
flat rear surface 6a of the frusto-conical portion 6 and
thus opposing any subsequent rearward movement of the
plunger 2.
This teherefore makes it no longer possible to draw
further liquid in, so making any second utilisation of the
syringe impossible. At the same time, with the extraction of
the needle, the cap 109 advances under the thrust of the
spring 112 into the configuration shown in Figure 10, in
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which it entirely encloses the needle, and the ends llOa of
the tongues 110 become inserted into the cavity 113, to
prevent any further advancement.
That wall of the cavity 113 located towards the rear
of the syringe is undercut, and the rear wall of the end
llOa of the tongues 110 is shaped to correspond to this
undercut. In this manner, the tongues oppose any force which
could tend to again move the cap 109 rearward, so keeping
the needle covered and preventing any accidental pricking by
the used needle.
As shown in Figure 11 and by an axis line in Figure 7,
the needle lOla can be formed with its axis inclined to the
axis of advancement of the cap 109, or in any event not
coinciding with the syringe axis. In this manner, when the
cap slides forward the needle undergoes deflection until it
is completely housed within the cap, where it then
straightens so that its point is displaced sideways from the
front hole lO9a of the cap 109, thus making any further
retraction of the cap 109 and consequent exposure of the
needle impossible, even under conditions of accidental or
voluntray breakage or bending of the tongues 110.
The dimensions of the syringe according to the
invention can be freely chosen according to utilisation
requirements, and materials of various types can be used
compatible with sterisability and absence of toxicity, and
compatible with the medicinal substances injected.
