Medical syringe abstract
The invention concerns a medical syringe comprising a tubular body,
in which slides a plunger comprising an opening, the plunger comprising
a sealing piece, movable in the plunger and which closes the opening
of the syringe before it is used. The assembly is arranged such
that, after the syringe has been used, the sealing piece no longer
closes the opening permanently, so that the syringe cannot be used
again. All the parts of the syringe are designed for being produced
by moulding and automatically mounted in series by axial jointing.
Medical syringe claims
What is claimed is:
1. Medical syringe comprising a tubular body, in which a piston
slides, the piston having an opening, a blocking unit blocking said
opening before the syringe is used, the blocking unit being arranged
to cooperate, when the piston reaches the end of its path, with
a counter-piece integral with the tubular body of the syringe, so
as to expel said blocking unit out of the opening in such a way
that after using the syringe the blocking unit definitively no longer
obstructs the opening so that the syringe cannot be re-used, wherein
the piston is arranged in such a way as to constitute an rigid inner
chamber inside which the blocking unit is housed, the whole being
arranged so as to impose a predetermined path on the blocking unit,
where the blocking unit has at one of its end a blocking head engaged
in the opening and at least one element arranged to prevent its
returning to its blocking position, said element resting prior to
the injection against the inner wall of said inner chamber, in such
a way as to generate a force of friction which is added to the force
exerted by the edge of the opening on the blocking head, so that
the pressure of the liquid acting on the blocking head during the
injection is insufficient to expel the blocking head out of the
opening, all the elements of the syringe being designed to be produced
by moulding and assembled on an automatic production line by axial
fitting.
2. Syringe according to claim 1 wherein the rigid inner chamber
comprises an intermediate element and a socket hooked with a notch
to the intermediate element, wherein the blocking unit is provided
at its rear section with locking elements capable of engaging on
an inner shoulder of the intermediate element when the piston reaches
the end of its path, thereby placing the locking elements in the
active position, and wherein the dimensioning of the assembly components
is such that, when mounting the assembly, the head of the blocking
unit can engage axially into the intermediate element, the socket
can be hooked to the intermediate element after positioning of the
blocking unit and the joint device once so assembled can be fixed
to the piston by forcing a cylindrical sleeve of the intermediate
element in a corresponding bore of the piston.
3. Syringe according to claim 2 wherein the locking elements comprise
at least one fin accommodating elastic deformation, whose free end
is directed towards the base of the body of the syringe and cooperates
with the wall of the inner chamber, said wall being designed so
as to allow the free end of the fin to slide against the wall of
the inner chamber when the blocking unit moves inside the chamber
after having come to a stop against the counter-piece but to then
prevent the sliding of the free end of the fin in the opposite direction.
4. Syringe according to claim 3 wherein the inner chamber comprises
a first space whose dimensions are chosen in order to maintain the
fin folded back along the blocking unit when the blocking head of
the blocking unit is blocking the opening and a second space whose
dimensions are chosen in order to allow the deployment of the fin
when the blocking unit has been moved inside the piston after coming
to a stop against the counter-piece.
5. Syringe according to claim 1 wherein the counter-piece comprises
at least one element forming a projection in relation to the base
of the tubular body of the syringe.
6. Syringe according to claim 2 wherein the counter-piece comprises
at least one element forming a projection in relation to the base
of the tubular body of the syringe.
7. Syringe according to claim 1 wherein the counter-piece is made
up of at least three lugs which project from the base of the tubular
body of the syringe, on the periphery of the orifice intended for
the injection of the liquid contained in the syringe.
8. Syringe according to claim 1 wherein the counter-piece consists
of a crenellated annular projection bordering the orifice intended
for the injection of the liquid contained in the syringe.
9. Syringe according to claim 1 wherein the counter-piece consists
of a washer with radial arms having, in the centre of the aforesaid
washer, a limit acting as a stop for the blocking unit.
10. Seal joint device coupled with the piston of a medical syringe
comprising a blocking unit which causes, by coming up against a
stop placed in the bottom of the syringe body, when the piston reaches
the end of its path, an irreversible deformation of the device so
as to exclude any possible reuse of the syringe, said blocking unit
being mounted into a guiding assembly coupled to the piston, wherein
the assembly itself comprises an intermediate element and a socket
hooked with a notch to the intermediate element, wherein the blocking
unit is provided at one end with a head provided with locking elements
capable of engaging on an inner shoulder of the intermediate element
and at the other end with a terminal part which, in active position,
closes an opening in the socket, but which is forced back by the
stop when the piston reaches the end of its path, thereby placing
the locking elements in the active position, and wherein the dimensioning
of the assembly components is such that, when mounting the assembly,
the head of the blocking unit can engage axially into the intermediate
element, the socket can be hooked to the intermediate element after
positioning of the blocking unit and the joint device once so assembled
can be fixed to the piston by forcing a cylindrical sleeve of the
intermediate element in a corresponding bore of the piston.
Medical syringe description
The present invention relates to a medical syringe made up of elements
allowing one injection but preventing the use of the same syringe
for any subsequent injection. In brief, this is a non-reusable syringe,
which self-destructs without special manipulation by the operator.
Naturally, for obvious reasons, hospital and medical environments
have for a long time been using disposable syringes which are used
once only. However these environments are not the only ones to use
syringes and trusting the user's self-discipline alone to ensure
once-only use is far from adequate in the real world. For example
it is well-known, according to WHO studies, that in developing countries
so-called disposable syringes are often re-used up to 50 times.
That is why numerous proposals have been made to make syringes
which, through-the way in which they are designed or constructed,
physically prevent their being used a second time.
The choice of the means to be adopted to this end is very limited.
In fact there is really only one way, namely fitting the chamber
of the syringe, basically the head of the piston, with a provisional
blocking unit which ensures that the chamber is sealed for the first
injection but which is definitively de-activated once the first
injection has been made.
The simplest version of this design is described in patent application
FR-A-2 606 643 relating to a syringe with an eccentric nozzle,
where the head of the piston is equipped with an orifice, initially
stopped with a moveable cork which is ejected from the chamber when
it encounters a centre punch when the piston reaches the end of
its path and the chamber reaches its minimum volume.
More sophisticated proposals have also been made, in particular
using a membrane held by the piston, which is then either displaced
by the pressure of the liquid or punctured at the end of the first
injection. Such proposals are to be found in European Patent 0345159
and in Patent application FR-A-2 606 643.
The number and variety of proposals of the prior art might suggest
that the problem has been fully dealt with. However this is not
so. In fact it is not sufficient to design a syringe which can function
on this principle or one of the many variants thereof, it then has
to be produced by an industrial process which entails a very low
cost. In this respect it should be remembered that the industrial
manufacture of syringes has to meet two requirements: first of all
the quantities are truly astronomical and amount to hundreds of
thousands of units in order to achieve simply a modest cost in this
context. Secondly, the syringes must be packed in high grade sterile
packaging, in spite of the enormous manufacturing output. It is
no doubt due to the fact that they did not comply with these two
conditions that the proposals of the prior art have not led to any
significant production, whereas the need is absolutely well-known
and absolutely urgent.
It is from this angle that the criticism of the previous proposals
should be made, since it is indeed the case that these proposals
do not meet the needs which the world is actually experiencing.
In order for a non-reusable syringe to truly meet the need, it is
necessary for the unit sale price to be at least comparable with
that of a conventional disposable syringe, but it is also necessary
for it to be equally reliable. It would actually be ridiculous to
allow major production initiatives if the physically unique nature
of the use were not guaranteed and remained uncertain, as is the
case with the proposals of the prior art.
The use of a membrane is disqualified in an industrial context
because these have to be plastic articles and therefore their elasticity
is an uncontrollable parameter, in particular over a period of time.
Therefore one cannot guarantee stable properties and thus one would
be exposed either to the impossibility of making the first injection
properly or to the uncertainty of preventing the second injection
in all cases. For example in the case of the syringe proposed in
European patent 0345159 because there is a flexible membrane at
the very end of the piston, the activation of the device is commanded
by the nature of the pressure exercised on the liquid to be injected.
The least drop in pressure may permanently disrupt the ongoing injection.
The use of an ejected cork is also to be ruled out because it is
a plastic article inserted in another and therefore one cannot truly
claim to be in control of the moment when the two parts will split
up. In other words, the cork may well pop out during the injection
simply due to the pressure of the liquid, and likewise it may be
ejected in the opposite direction when the liquid is sucked into
the syringe. In any case nobody can guarantee that it will not pop
out and this is a disadvantage.
The aim of the present invention is thus to propose a non-reusable
syringe, whose constituent elements, and the properties thereof
in combination with one another, allow on the one hand economical
and reliable industrial production and, on the other hand, guarantee,
through the controllable mechanical properties of the aforesaid
elements, that it really can be used only once.
To this end, the present invention relates to a medical syringe
comprising a tubular body, in which a piston slides, the piston
having an opening, a blocking unit blocking said opening before
the syringe is used and this blocking unit arranged so as to cooperate,
when the piston reaches the end of its path, with a counter-piece
integral with the tubular body of the syringe, so as to expel said
blocking unit out of the opening in such a way that after the syringe
has been used the blocking unit can definitively no longer stop
up the opening, so that the syringe cannot be re-used. The piston
is arranged in such a way that an inner chamber is constituted,
inside which the blocking unit is housed, the whole being arranged
such that a predetermined path is imposed on the blocking unit,
without the use of a distorting element, and the blocking unit has
a blocking head engaged in the opening and at least one element
arranged so as to prevent its returning to its blocking position.
The latter element, before the injection, rests against the inner
wall of said inner chamber, so as to generate a force of friction
which is added to the force exercised on the blocking head by the
edge of the opening, such that when the pressure of the liquid is
exercised on the blocking head during the injection it is not sufficient
to expel the blocking head out of the opening. All the elements
of the syringe are designed such that they can be produced by moulding
and fitted on an automatic production line using axial fitting.
In one embodiment of the syringe, the back part of the blocking
unit comprises at least one fin which will tolerate an elastic deformation
and the free end of which is directed towards the bottom of the
syringe body and cooperates with the wall of the inner chamber.
The wall of the inner chamber is arranged so as to allow the free
end of the fin to slide against the wall of the inner chamber when
the blocking unit moves inside the chamber after coming to a stop
against the counter-piece but so as then to prevent the free end
of the fin sliding in the opposite direction.
The inner chamber may comprise a first space whose dimensions are
chosen so as to keep the fin folded back along the blocking unit
when the head of the blocking unit is blocking the opening, and
a second space whose dimensions are chosen so as to allow the fin
to be extended when the blocking unit has been moved inside the
piston after hitting the counter-piece.
According to one preferred embodiment, the counter-piece comprises
at least one unit which projects from the bottom of the tubular
body of the syringe .
Other characteristics, aims and advantages of the invention will
emerge more clearly in the light of the description of one embodiment
of the syringe and the variants, set out below by way of example
and illustrated
by the drawings appended in which:
FIG. 1 is an axial section of the front part of a first embodiment
of the syringe, as it appears before or during the injection;
FIG. 2 is a similar section to that of FIG. 1 of the front part
of the same syringe, as it appears after an attempt to re-use it;
FIG. 3 is an axial section of the front part of a second embodiment
of the syringe, as it appears before or during the injection;
FIG. 4 is a similar section to that of FIG. 3 of the front part
of the same syringe, as it appears after an attempt to re-use it;
FIGS. 5 to 7 are partial axial sections of the front end of the
syringe showing three versions of the counter-piece which acts as
a stop for the blocking piece; and
FIG. 8 is an axial section of the front part of a variant embodiment
of the syringe, the half-section on the right represents the syringe
before the injection and the half-section on the left represents
the syringe after the injection.
The syringe shown in FIGS. 1 and 2 comprises a tubular body 1
at the end of which is a nozzle 1a intended to receive a hypodermic
needle. A piston activated with the help of a rod 2 slides along
in this tubular body. This rod, cross-shaped, ends in an element
2a shaped like a socket.
The piston has an intermediate element 3 of which the top part
3a, in the form of a sleeve, is forced by axial fitting into the
element 2a. An element 4 in the shape of a socket, hooks with a
notch on to the intermediate element 3. This element 4 has on the
one hand an outer bead 4b which is supported against the inner face
of the tubular body 1 in order to ensure a seal between the piston
and the tubular body and on the other hand a base 4a which is in
contact with the liquid 8 to be injected and transmits the thrust
of the piston to it.
The piston comprises an inner chamber whose space is bounded by
the internal faces of elements 3 and 4 thus linked together. The
intermediate element 3 comprises a lower part 3b defining a lower
cylindrical space and an adjacent upper part 3a defining an upper
cylindrical space, the diameter of the lower cylindrical space being
less than that of the upper cylindrical space so as to constitute
a shoulder 3c at the junction of the two parts 3a and 3b. Vents
have been made within the element 2a in order to adjust the pressure
inside the inner chamber to atmospheric pressure.
The base 4a of the element 4 is pierced in the centre by an opening
5 in which the front terminal part 6a is engaged, hereafter called
the blocking head 6a of a blocking unit 6. This blocking unit, essentially
cylindrical in shape, is housed within the inner chamber of the
piston so that its axis of symmetry is superimposed on that of the
syringe. The blocking unit is fitted so that it can slide along
the walls of the lower part 3a of the intermediate element. It ends,
at its rearmost extremity, in a head 6b which has two elastic fins
6c directed towards the front, diametrically opposite one another
and held in place before or during a first injection in the position
shown in FIG. 1. The dimensions of the blocking head 6a, shaped
like a truncated cone, are such that it can settle and slide within
the opening 5 whilst ensuring a perfect seal. For example, in the
case of a syringe designed to enable the injection of a maximum
volume of 2.5 ml of liquid, the opening has a diameter of 2 mm,
the truncated cone of the blocking head has a smaller section, whose
diameter is equally 2 mm and an upper section whose diameter is
2.5 mm. The blocking head 6a is surmounted by a crown 7 which projects
laterally, acting on the one hand as a stop for the positioning
of the blocking unit inside the inner chamber and on the other hand
helping to seal the aforesaid inner chamber.
The tubular body 1 of the syringe comprises a counter-piece 10
integral with its base 1b, close to the nozzle 1a. This counter-piece
comprises lugs 10a which project in relation to the base 1b and
which are arranged so that they are located on the extension of
the blocking head 6a of the blocking unit, whilst allowing sufficient
room for the liquid to be injected. This counter-piece will be explained
in detail later.
As can be seen in FIG. 1 the two fins 6c are supported on the
walls of the lower part 3a defining the lower cylindrical space.
The diameter of this cylindrical space is such that the fins are
folded back there, constrained, along the blocking unit.
When the piston is activated, it exercises pressure on the liquid
contained in the body which is then ejected through the nozzle 1a.
The forces of friction, exercised both on the fins and on the blocking
head 6a of the blocking unit, are such that the pressure which the
liquid can exercise on this head is not sufficient to cause the
blocking unit 6 to slide.
When the piston reaches the end of its path, the blocking unit
6 comes into contact, via its head 6a, with the lugs 10a of the
counter-piece 10 which then acts as a stop. Continuing its path
until it reaches the base 1b of the syringe, the piston becomes
caught on the counter-piece 10 which drives the blocking head 6a
out of the opening 5 then the blocking unit moves inside the inner
chamber of the piston, and fins 6c slide along the walls of the
lower part 3b of the intermediate element 3 after which the fins
are extended inside the upper cylindrical space constituted by the
upper part 3a of the intermediate element when their ends pass the
shoulder 3c.
The blocking unit is then in the position shown in FIG. 2 the
elastic fins 6c are extended in a configuration which renders them
more stable and supported on the walls of the upper part 3a, being
blocked by the shoulder 3c, thus making it impossible for the blocking
unit to return to its initial position, so that the blocking unit
definitely no longer blocks the opening 5.
This arrangement means that it is no longer possible to suck up
liquid again. In fact, through the release of the opening 5 the
inside of the body of the syringe is in communication with the inner
chamber of the piston and in turn is adjusted to atmospheric pressure.
The piston, through a backward movement, is no longer able to create
a negative pressure there.
The variant shown in FIGS. 3 and 4 only differs from the first
embodiment in the arrangement of the blocking unit 6. In this variant
the blocking unit 6 comprises only one elastic fin 6c, but its structure
and function are identical with those of the two fins on the blocking
unit if the preceding embodiment.
The presence of this single fin makes the blocking unit asymmetric.
Consequently, once the blocking head 6a is forced to move out of
the opening 5 the blocking unit 6 pivots on itself under the influence
of the thrust of the fin against the wall of the lower part 3b.
As FIG. 4 shows the blocking unit then definitively loses its alignment
with the opening 5 and is no longer able to block it again.
As FIGS. 1 to 4 show, the counter-piece 10 comprises three lugs
10a which project from the base 1b of the tubular body into the
extension of the inner walls of the nozzle 1a. The height of the
lugs 10a is chosen so as to cause sufficient displacement of the
blocking unit inside the inner chamber of the piston, when the piston
reaches the end of its path, as to enable the fins 6c to be deployed
inside the upper cylindrical space constituted by the upper part
3a of the intermediate element, as described above.
According to the variant shown in FIG. 5 the counter-piece 10
is made up of an annular projection 1c provided in the centre of
the base 1b of the tubular body of the syringe. This projection
1c is crenellated, which creates passages 12 allowing the liquid
contained in the syringe to pass into the nozzle 1a when the blocking
head 6a of the blocking unit is supported on the aforesaid projection.
In the variant shown in FIG. 6 the base 1b of the tubular body
1 of the syringe has in the centre a washer 10b with radial arms
10c ending in a central contact point or limit 10a in the form of
a lug against which the blocking head 6a stops when the piston reaches
the end of its path. The size of this contact point 10a is chosen
so as to obtain the effects described above. The washer is inserted
in the mass of the syringe body and supported partly on the opening
of, the nozzle 1a. The space between the radial arms is sufficient
not to obstruct the passage of the liquid to be injected.
The variant shown in FIG. 7 differs from the preceding variant
in the shape of the central washer 10b, placed on the base 1b of
the tubular body of the syringe. This washer has radial arms 10c
carrying a central contact point 10b against which the blocking
head 6a stops when the piston reaches the end of its path. This
version offers the advantage that the washer may be arranged on
the base of any already existing conventional syringe.
As shown in FIGS. 1 to 4 the element 4 is hooked on by a notch
to the intermediate element 3. In order to facilitate assembly,
which is carried out by axial fitting, the element 4 is preferably
made of a semi-rigid or flexible plastic material, for example synthetic
rubber.
In one variant embodiment, shown in FIG. 8 the element 4 is made
of a rigid plastic material.
The assembly described and shown is easy to manufacture, since
all the elements can be simply moulded from plastic and easily assembled
by an axial fitting system, allowing of large scale industrial production,
in particular automated mass production, for example using automatic
carousels, since the assembly of the various parts of the syringe
does not require any relative angular positioning. Moreover, the
design of the syringe as per the invention also allows the use of
the traditional components of a so-called "triple body"
syringe, comprising a cylinder, a piston and a connecting piece.
Moreover the functioning of the syringe as per the invention is
absolutely reliable since the displacement of the blocking unit
to bring it to its released position is caused only when the piston
reaches the end of its path, which means among other advantages
that it is possible to inject the whole of the liquid contained
in the syringe. |