Abstrict A disposable syringe with an automatically retractable hypodermic
needle of the type consisting of an injector plunger, a container
cylinder with needle-carrier head and a needle with connection ferrule.
The ferrule is housed in an inner hollow of the head of the cylinder,
wherein the tube of the needle has passing axially though it a guiding
channel to the outside, the hollow having a plurality of elastic
retention tabs and the rear face of the needle-carrier head of the
cylinder being in contact with an elastomeric washer interposed
in an annular manner between it and the plunger which is defined
by a cover whose attack front part has a slightly conical circular
crown coinciding with said elastomeric washer and which is equipped
centrally with a frustoconical core coinciding in a closely fitting
manner with the opening of the ferrule of the needle. The cover
also has a perimeter groove on its surrounding face which can be
locked in terms of position in a plurality of domed projections
of the inner wall of the tube which contains it, thereby forming
the shaft of the plunger, the head of the cover and the base of
said shaft being joined together by a tensioned elastic means and
comprising, in the rear zone of their surrounding wall, a plurality
of grooves in the rear zone which link its inside to the outside
space.
Claims We claim:
1. A disposable syringe with an automatically retractable hypodermic
needle of the type consisting of an injector plunger, a container
cylinder with needle-carrier head and a needle with connection ferrule,
wherein said ferrule is housed in an inner hollow of the head of
the cylinder, wherein the tube of the needle has passing axially
through it a guiding channel to the outside, said hollow having
a plurality of elastic retention tabs and the rear face of the needle-carrier
head of the cylinder being in contact with an elastomeric washer
interposed in an annular manner between it and the plunger which
is defined by a cover whose attack front part has a slightly conical
circular crown coinciding with said elastomeric washer and which
is equipped centrally with a frustoconical core coinciding in a
closely fitting manner with the opening of the ferrule of the needle,
said cover also having a perimeter groove on its surrounding face
which can be locked in terms of position in a plurality of domed
projections of the inner wall of the tube which contains it, thereby
forming the shaft of the plunger, the head of the cover and the
base of said shaft being joined together by a tensioned elastic
means and comprising, in the rear zone of their surrounding wall,
a plurality of grooves in the rear zone which link its inside to
the outside space.
2. A disposable syringe with an automatically retractable hypodermic
needle as claimed in claim 1 wherein the guide orifice of the tube
of the needle has a transverse elastic membrane which can be perforated
by the discharge tube of the needle.
3. A disposable syringe with an automatically retractable hypodermic
needle as claimed in claim 1 wherein the frustoconical tip of its
plunger has a plurality of longitudinal grooves in its outer face,
providing communication between the chamber of the cylinder and
the opening of the ferrule of the needle when the latter comes into
contact with said frusto-conical tip.
4. A disposable syringe with an automatically retractable hypodermic
needle as claimed in claim 1 wherein the tube of the plunger has
an external diameter which is reduced over its rear portion and
has at least one through-orifice, in its surrounding wall, positioned
close to its distal end.
Description The present patent of invention, which is now being filed, the
relevant registration being applied for, relates to a disposable
syringe, with an automatically retractable hypodermic needle, which
is suitable for injecting medicinal substances and/or taking samples
of blood and liquids in general, in human or veterinary medicine,
with the particular functional characteristic of, once the operation
has been completed, producing, by means of a slight additional pressure
at the end of the path of the plunger, the automatic firing of the
needle in the entering direction, said needle remaining definitively
inside it so as to guard against pricking the person handling it
and to prevent the latter coming into contact with pathogenic substances
which still remain unused, to prevent reuse.
After the procedures referred to above, hypodermic needles usually
remain wedged in the ejector tips of the syringes, representing
a significant risk of infection for persons responsible for handling
them, since combined with their capacity to graze is the fact that
they retain dangerously contaminating residues. To protect the staff
involved, use is made of container receptacles designed to remove
them and store them inside, after which they are transported with
other residues for incineration in specially constructed furnaces.
However, such operations continue to pose a risk because disposal
is not immediate, especially in operating theaters where the surgeon
involved is concentrating his attention on the operating area, involuntarily
taking his attention away from the action of disposing of said elements
once they have been used. Moreover, those responsible for removing
the containers referred to are exposed to subsequent accidents owing
to the fact that uncovered needles usually pass through their walls
and to the fact that the actual operation of inserting them or placing
a cap on them represents an additional risk.
Another potential act which poses a threat to the required aseptic
measures arises from the fraudulent act which may be committed by
any person attempting to reuse syringes with a needle, causing severe
harm to subsequent patients which is beyond the control of those
responsible.
In view of the aforesaid, it would appear ideal to have a syringe/needle
unit which can be deactivated definitively and without the possibility
of being rearmed, the needle being protected immediately at the
end of the plunger's path, as part of the operation.
In precise terms, the disposable syringe with an automatically
retractable hypodermic needle, which is the subject of the invention,
tends to optimize the use of such elements, overcoming the drawbacks
mentioned and complying with the ideal conditions mentioned in the
above paragraph.
Specifically, this is a syringe formed by a hollow cylinder within
which the corresponding plunger slides in a closely fitting manner,
equipped, respectively, with rear gripping fins and outer thrust
enlargement, as in conventional syringes. Said cylinder is notable
in that, at its actuator end, it has a needle guide with a projecting
axial cylindrical orifice and, on the inside, a core with a frustoconical
hollow equivalent to the connection ferrule thereof with elastic
retention tabs at its major base and an elastomeric washer on which
the head of the plunger is seated.
Said plunger, for its part, is a hollow cylinder whose particular
form arises from the fact that it has a blind attack end formed
by a cover which is grooved at the perimeter on its outer surrounding
face, said groove fixing its original position, on domed embossments
of the inner face of the tube containing it, being retained axially
at its end by an annular entrant flange of the latter. The attack
front part of said cover is a circular crown with a slight conicity
which coincides with the elastomeric washer of the container cylinder,
with a blind frustoconical tip, equivalent to the opening of the
connection ferrule of the needle, while, on the inside, said cover
is joined to the base of the plunger by means of an elastic means
which is tensioned in its original position.
The unit described is presented, for use, with the hypodermic needle,
projecting via its end, covered by a standard cap, with its connection
ferrule positioned in the cavity of the core of the cylinder of
the syringe and retained by the elastic tabs with no possibility
of backward movement, while the plunger is seated with its attack
front part on the corresponding face of the elastomeric washer with
its frustoconical tip facing the opening of the needle without penetrating
totally into it. In order to pick up the substance to be injected
from its container or to remove biological samples, the plunger
is slid along in the same way as in known syringes, the protective
needle cap previously having been removed. In order to inject the
medicinal substance or to deposit the sample removed into laboratory
test tubes, the procedure is also as with known syringes, i.e. the
plunger is pushed in the entering direction as far as the end of
its path, its attack front part being again in contact with the
elastomeric washer. This arrangement leads to actuation of the novel
security device, merely by exerting a pressure which is slightly
greater than that required by the previous operation, as a continuation
thereof. This gives rise to squashing of the elastomeric washer
and therefore the travel of the plunger continues until its frustoconical
tip is inserted into the connection ferrule of the needle, wedging
itself securely. As a result of precise dimensioning, said frustoconical
tip, at the end point of its displacement, causes the total opening-out
of the tabs for retaining the needle which, given their contact
edge, which has a slope similar to that of the frustoconical tip,
allow their insertion and transverse folding, by means of elasticity,
toward coincident hollows of the core. At this point, the slight
residual advance which the elastomeric washer allows the cylindrical
tube of the plunger wedged inside the ferrule of the needle brings
about the disconnection of the perimeter groove of the cover and
the domed reliefs of the tube, leaving the cover exposed to the
retractile force of the elastic means joining to the base, entraining
the needle inward in a definitive manner. The retractile displacement
of the needle takes place strictly linearly on account of the fact
that it is guided in a stable manner by the tube of the plunger
vis-a-vis the cover to which it is secured and, at the beginning,
also by the guide of the cylinder.
Without altering the functional principle described, which in itself
constitutes the novel advantage of the present invention, complementary
alternatives which enhance its efficiency are envisaged in the form
of the inclusion of an elastic membrane, positioned in the needle
guide, which is perforated by the tube of the needle and, when the
needle is withdrawn, acts, given the elasticity of its material,
as a valve to retain the minute amount of liquid which may have
been left inside it; the presence of longitudinal grooves on the
surrounding face of the frustoconical tip of the plunger which allows
the total passage of liquid to the tube of the needle, when the
latter has been wedged; and a reduction in the external diameter
of the tubular body of the plunger in its distal portion so as to
reduce its zone of friction with the syringe cylinder, thereby creating
between both of them a chamber which communicates with the outside
via its distal end and with the inside of the plunger through orifices
in its tubular wall in order to give rise to a rapid escape of the
air which is compressed on account of the rapid backward movement
of the cover.
In order to give material form to the advantages discussed briefly
in this way and in order to facilitate understanding of the structural
and functional characteristics of the disposable syringe with an
automatically retractable hypodermic needle, a description is given
below of a preferred embodiment and of variants which are illustrated
diagrammatically and without a specific scale on the attached sheets,
with the express clarification that, precisely because this is an
example, it cannot be attributed a limiting or exclusive nature,
its purpose simply being to be a mere illustration of the basic
underlying design.
FIG. 1 is a sectional view through a radial plane of the invented
unit, with its components positioned as presented for use;
FIG. 2 is a view equivalent to the previous view, with the plunger
at the end of its path and the safety device about to be fired;
FIG. 3 is a view equivalent to the above views, with the safety
device being actuated;
FIG. 4 shows, in two details, indicated as A in FIG. 1 the behavior
of the elastic membrane positioned in the needle guide and proposed
as a complementary variant, together with the drainage grooves made
in the frustoconical tip of the plunger;
FIG. 5 shows a syringe like the invented syringe, with a plunger
which has a reduced diameter in its rear portion and a complementary
air-escape orifice.
In all the figures, the same or equivalent parts or elements which
make up the chosen unit as an example for the present explanation
correspond to identical reference numbers.
As shown in FIG. 1 the unit is presented with the needle 1 projecting
via the guide 2 of the cylinder 3 with its protective cap 4 and
its connection ferrule 5 housed in the hollow 6 retained by the
elastic tabs 7 of which only one is shown in the figure, capable
of folding in the radial direction into the cavities 8. The plunger
9 for its part, is presented with its cover 10 locked by means
of its perimeter groove 11 on the domed projections 12 and its attack
front part resting on the elastomeric washer 13 the frustoconical
tip 14 partially inserted into the opening of said ferrule 5 remaining
in this position without being in contact with the ferrule or with
the tabs 7. Between said cover 10 and the base 15 of the plunger
is the elastic means 16 under tension.
Injection of the medicinal liquid having taken place by means of
customary actuation, or the extracted material having been discharged
into the relevant test tubes, the syringe returns to the initial
position (FIG. 1) and, through the effect of an additional pressure
in the direction F, as may be seen in FIG. 2 the elastomeric washer
13 is squashed, thereby allowing the plunger to advance until its
frustoconical tip 14 is secured in the ferrule 5 by means of wedging,
opening up the tabs 7 to release the ferrule at the same time as
the cover 10 reaches the limit of its path, although its container
tube is able to squash said elastomeric washer further, this counter-positioning
of effects bringing about disconnection of the perimeter groove
11 from the domed projections 12 said cover being retracted through
the action of the elastic means 16 entraining the needle 1 with
it which remains housed definitively inside the tubular body of
the plunger 9. During the rapid retractile actuation described,
the mass of air contained between the head of the cover 10 and the
base of the plunger 15 escapes via the grooves 17.
FIG. 3 shows the behavior of the cover in its backward movement,
its escape of air and the distension of the elastic means 16 the
unit being in such a condition that it may be disposed of and is
risk free.
In the sequence illustrated in FIG. 4 it is possible to see the
membrane 18 through which the tube of the needle 1 passes and which
later seals off the guide orifice when the guide has moved away,
the first diagram also showing the presence of the grooves 19 for
draining off the minimal remains of liquid retained at the end of
the path of the plunger.
The contents of both the preceding figure and of FIG. 5 show the
complementary alternatives offered, the last figure demonstrating
a plunger with an external section which is reduced over its distal
portion, which reduces the friction surface between it and the cylinder
of the syringe, forming, by addition, a cylindrical chamber 20 which
can be used to allow more air to exit via the orifices 21 of the
body of the plunger.
When implementing the disposable syringe with an automatically
retractable hypodermic needle, which is described and illustrated
by examples, it will be possible to incorporate modifications which
must be regarded as variant embodiments included within the scope
of protection of the present patent of invention, said scope being
defined, fundamentally, by the text of the following claims. |