Abstrict A disposable syringe with an automatically retractable hypodermic
needle for use in the injection of medicinal substances and/or the
removal or samples of blood and liquids in general in human or veterinary
medicine is disclosed. Once the operation of the syringe is performed
the application of slight additional pressure to the end of the
piston's travel causes the needle to be automatically shot inwards,
with it remaining permanently housed in the interior in order to
protect the operator from pricks or contact with pathogenic substances,
and also making it unusable for subsequent applications.
Claims We claim:
1. A disposable syringe with an automatically retractable hypodermic
needle, comprising:
an outer tube having an internal diameter and a forward housing
defining an inner front wall face and a coupling end, a piston in
the outer tube and having a hollow tube shank, at least a posterior
section of the shank having a diameter less than the internal diameter
of the outer tube, and an annular working face movable toward the
inner front wall face of the outer tube,
a needle holder connected to the coupling end of the outer tube,
the needle holder having a distal guide conduit,
a hypodermic needle in the distal guide conduit of the needle holder
and having a coupling nipple wedged in a posterior axial portion
of the needle holder,
an annular elastomer washer housed between the inner face of the
front wall of the outer tube and the working face of the piston;
a plug in the annular working face of the piston, the plug having
a perimetral projection caught posterially by small internal projections
in the hollow tube shank and having a forward capturing tip of frustoconical
shape matching the coupling nipple of the needle, the hollow tube
shank having at least one orifice providing fluid communication
between the plug and the hollow shank exterior, and
elastic means linking the plug and the piston and placed in tension
in a position of maximum compression of the annular elastomer washer.
2. A disposable syringe with an automatically retractable hypodermic
needle as claimed in claim 1 wherein the coupling end of the outer
tube includes an internal stop and internal retaining tongues spaced
by an axial distance outwardly from the internal stop, and wherein
the needle holder has an outer perimetral step of an axial length
equivalent to the axial distance spacing between the internal stop
and the internal retaining tongues.
3. A disposable syringe with an automatically retractable hypodermic
needle as claimed in claim 1 wherein the distal guide conduit has
a transverse elastic absorbent membrane.
4. A disposable syringe with an automatically retractable hypodermic
needle as claimed in claim 1 wherein the capturing tip of the plug
has an outer surface scored by a plurality of longitudinal grooves.
5. A disposable syringe with an automatically retractable hypodermic
needle as claimed in claim 1 wherein the needle holder has at least
one elastic retaining tongue at a posterior edge opposite an opening
edge of the coupling nipple.
6. A disposable syringe with an automatically retractable hypodermic
needle as claimed in claim 1 wherein the needle holder is an integral
part of the forward housing of the outer tube.
7. A disposable syringe having an automatically retractable hypodermic
needle as claimed in claim 1 having a circular transverse cross
section and the hypodermic needle located centrally.
8. A disposable syringe having an automatically retractable hypodermic
needle as claimed in claim 1 having a circular transverse cross
section and the hypodermic needle located eccentrically, and including
longitudinal guide means extending from the piston to the outer
tube and another longitudinal guide means extending from the outer
tube to the piston.
9. A disposable syringe with an automatically retractable hypodermic
needle as claimed in claim 1 having an elliptical transverse cross
section and the hypodermic needle located centrally.
10. A disposable syringe with an automatically retractable hypodermic
needle as claimed in claim 1 having an elliptical transverse cross
section and the hypodermic needle located eccentrically.
11. A disposable syringe with an automatically retractable hypodermic
needle as claimed in claim 1 having an elliptical transverse cross
section and a concavity in one of the major dimensions.
Description BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a disposable syringe with automatically
retractable hypodermic needle, for use in the injection of medicinal
substances and/or the removal of samples of blood and liquids in
general in human or veterinary medicine, with the special feature
that once the operation is performed the application of slight additional
pressure to the end of the piston's travel causes the needle to
be automatically shot inwards, with it remaining permanently housed
in the interior in order to protect the operator from pricks or
contact with pathogenic substances, and also making it unusable
for subsequent applications.
2. Description of the Related Art
In the procedures mentioned hypodermic needles are normally fitted
to syringes and represent a great hazard of infection to those persons
responsible for their subsequent handling, not only because of their
ability to prick, but also because they retain contaminating residues.
In order to protect operating personnel from these risks, in practice
containers are used which are designed to capture and store these
units, which are then transported to incinerators for total destruction.
However these operations are risky because disposal does not take
place immediately, especially in operating theaters in which the
operating surgeon's attention is concentrated on the operating field,
and little attention is involuntarily paid to the disposal of such
units once used. On the other hand, those responsible for removing
the containers mentioned are exposed to accidents given that the
uncovered needles can pass through their walls and the operation
of placing them in a protective cap represents an additional risk.
There is also the possibility that someone committing a fraudulent
act might reuse the syringes disposed of, causing severe harm to
subsequent patients.
Various types of hypodermic syringes with a retractable needle
which are intended to overcome the disadvantages described, which
have a functional behavior which differs from that described herein,
are known. Nevertheless those which are most widely known will be
mentioned above, pointing out their obvious differences.
These are U.S Pat. Nos. 5152750 5180370 5222944 5382235
5578015 and 5616134 which form a group with nonautomatic retraction.
U.S. Pat. No. 5190526 which requires great complexity in fitting
of the piston, given that this must disassemble, in order to break,
into a plug which is retained at the working front and a retracting
capture unit, with the disadvantage that there is no possibility
of fitting and removing the needle from the exterior, nor of retaining
the residual liquids which normally remain at said front; on the
other hand the needle used has to be manufactured specially only
for this mechanism. U.S. Pat. No. 5324265 which is merely an
improvement on the above, which converts it into a syringe with
an externally removable needle, but retains the other disadvantages
mentioned. U.S. Pat. No. 5320606 in which the member acting as
a piston slides externally until its edge produces an opening for
a seal which holds the needle-holding tip in position, which is
integral with an elastomer member which controls the passage of
liquids; the elastic condition required of this tubular member represents
a construction problem in the region in which it is incorporated
with the needle holder and, at its other end, with the end of the
tube containing it; furthermore, the positioning of the fin for
fixing this syringe, which is so close to its working front, makes
it inconvenient to handle. U.S. Pat. No. 5656031 which has a
breaking and retraction mechanism initiated by the pusher of an
external protector, which gives rise to risks in application and
our U.S. application Ser. No. 09/005681 which is fundamentally
distinguished by the manner in which it captures the needle and
its capturing mechanism, which does not permit the option of external
mounting.
SUMMARY OF THE INVENTION
This invention is intended to go beyond the design of those mentioned,
providing greater constructional simplicity and functional efficiency.
In particular, it relates to a syringe comprising a hollow tube
within which the corresponding piston slides tightly, equipped respectively
with posterior fins which receive and spread the external push as
in conventional syringes. The hollow tube mentioned has a cylindrical
mouth at its operating end with an internal annular step and elastic
retaining tongues arranged internally in the vicinity of the edge
thereof, forming a housing which is capable of supporting a needle
for injection and extraction. This latter component, which is incorporated
with the whole, is a tubular body with a posterior widening forming
a cylindrical section which is introduced into the housing mentioned
above, overcoming the elasticity of the tongues and abutting against
the annular step in order finally to be retained by the return of
the latter to their initial position. At its posterior opening the
needle holder has an axial frustoconical cavity which coincides
with the external shape of the coupling nipple of a standard needle
which is extended to its end in a cylindrical duct, guiding the
needle tube, positioned with said coupling nipple wedged in the
space mentioned. For its part the duct described has a transverse
seal of absorbent elastic material through which the needle tube
passes, which is capable of absorbing liquids from its outer surface
and closing it off when it is retracted. The difference in surface
area between the cross section of the hollow tube and the cylindrical
mouth holding the needle holder gives rise to a first front wall
against which there is fitted internally an elastomer washer placed
between it and the end of the piston. The latter is a tube having
an axially slidable front section with a leaktight fit with respect
to the outer hollow tube and a reduction in the same in its posterior
part to reduce friction. At the front the piston in question is
blind, as a consequence of a terminal needle capture device fitted
flush with its front edge and held from a sealing perimeter projection
by elastic tongues within it. Up to the working end the capture
device mentioned extends as a frustoconical tip equivalent to the
internal empty volume of the coupling nipple of the needle, against
which it abuts axially, being linked by its rear face to the base
of the piston by elastic means which is under tension in its original
position.
The base of the piston is closed off by an integral plug which
with its peripheral outer widening forms the pushing means. To complete
the description of the construction the piston is provided with
escape openings from its internal chamber in its distal portion
and, without this constituting an excluding condition, the outer
cylinder may be fitted with ends on its inner enclosing wall which
prevent rearward movement of the enclosure sealing the piston at
the end of its travel, preventing it from being uncoupled on opening;
longitudinal channels in the capturing tip which provide for complete
drainage of the compressed liquid when this is wedged in the coupling
nipple of the needle, or said channels may be made in the latter
and secondary elastic catches which help to hold the needle in the
needle holder.
The assembly described is presented for use with the hypodermic
needle wedged in the needle holder, where it may be further retained
by means of the secondary elastic tongues mentioned and is optionally
mounted on or separate from the outer body of the syringe, given
that the piston lies with its working front on the corresponding
face of the elastomer washer with its capturing tip opposite the
opening of the needle when this has been fitted, without penetrating
it totally.
For taking up the injectable substance from its container or extracting
biological samples the piston is moved in the same way as in known
syringes, after removal of the protective cap.
To inject a medicinal substance or to place the sample extracted
in laboratory test tubes the procedure is again the same as with
known syringes, that is, the piston is pushed down to the end of
its travel, so that its front end is again in contact with the elastomer
washer. From this point access is available to operation of the
novel safety device merely by exerting slightly greater pressure
than that required for the previous procedure, continuously with
it; this causes the elastomer washer to be flattened by the end
of the piston tube until the capturing tip is introduced into the
coupling nipple of the needle and becomes firmly wedged within it.
As a consequence of accurate dimensioning said frustoconical tip
encounters a stop to its progress. At this point the slight residual
advance which the elastomer washer allows the piston tube brings
about breakage of the annular projection of the capturing end with
respect to the elastic tongues within it, leaving it exposed to
the retractile force of the elastic medium, which pulls the needle
permanently inwards, given that the firmness with which the capturing
tip is wedged in the coupling nipple overcomes the relationship
between the latter and the needle holder.
The retractile movement of the needle takes place linearly, until
it disappears from the exterior, guided by the needle holder, and
in its travel the absorbent membrane prevents residual liquid from
dripping from its enclosing surface.
Without altering the functional principle described, which constitutes
the present invention, the following alternative variants have been
considered:
a) A syringe like that described, in which the needle is originally
fitted internally, without possibility of leaving from the front,
in which case the needle holder constitutes an extension which is
integral with the working end of the outer tube.
b) A syringe such as that described or as described in alternative
a) (both cylindrical) with the axis of the needle and its capture
mechanism being displaced from the center, so that a longitudinal
channel will be necessary in one of its tubular components, coinciding
with an equivalent longitudinal projection in the other, acting
as a guide so that said capture mechanism operates in the same line
as the needle, and another similar guide means linking the inner
tube with the capturing end.
c) A syringe as described or as mentioned in alternative a) having
an elliptical transverse cross section and a central needle.
d) A syringe as described or as mentioned in alternative a) having
an elliptical transverse cross section and a needle which is displaced
from its center, coinciding with its capture mechanism.
e) A syringe as described or as mentioned in alternative b), having
an anatomical cross section determined by an ellipse, with one of
its major lengths transversely concave.
BRIEF DESCRIPTION OF THE DRAWINGS
To give physical form to the advantages which have been merely
mentioned and in order to aid understanding of the constructional
and functional features of this disposable syringe with an automatically
retractable hypodermic needle, a description is provided below of
a preferred embodiment and variants which are illustrated diagrammatically
and without any specific scale in the appended drawing figures,
with the express clarification that as this is specifically an example,
no restrictive or exclusive character should be assigned to it,
its purport being merely illustrative of the fundamental concept
on which it is based.
FIG. 1 is a longitudinal cross section of a syringe according to
the invention with an external needle in the confirmation of its
original position.
FIG. 2 is a figure equivalent to the above with the piston at the
end of its compression stroke.
FIG. 3 is a figure equivalent to the above with excess pressure
applied to the piston and the capture device and the needle retracted.
FIG. 4 is a partial cross section of a needle holder separated
from the syringe.
FIG. 5 is a view equivalent to the above of a needle holder with
a secondary retention catch.
FIG. 6 is a view equivalent to the above from the end of a syringe
with the needle incorporated internally.
FIG. 7 is a diagrammatical representation of the transverse cross
section of a cylindrical syringe with a central needle.
FIG. 8 is a view equivalent to the above of a cylindrical syringe
with an eccentric needle.
FIG. 9 is a view equivalent to the above of a syringe with an elliptical
cross section and a central needle.
FIG. 10 is a view equivalent to the three above of a syringe with
an elliptical cross section and an eccentric needle.
FIG. 11 is an equivalent view to the four above of a syringe having
an elliptical cross section with a concave length and a central
needle.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In all the figures, identical reference numbers correspond to the
same or equivalent parts or structural elements of the assembly
taken as an example for this explanation.
In FIG. 1 which shows a syringe for injection and extraction,
it will be seen that a hypodermic needle 1 is fitted in needle holder
2 into which it is introduced through its posterior opening until
it is retained by being wedged on its coupling nipple 3. This needle
holder is retained in the forward housing of outer tube 4 between
posterior terminal seat 5 and elastic tongues 6. Compressor piston
7 comprising inner tube 8 and outer capture device 9 with its capturing
tip 10 is in this figure in unpressurized contact with elastomer
washer 11 which is located between this and the front wall of said
outer tube 4. Under these conditions capturing tip 10 is inserted
into coupling nipple 3 but is not in contact with it.
In the following sequence, shown by FIG. 2 the piston has moved
forward, slightly compressing elastomer washer 11 to a point such
that it enables tip 10 to be wedged in nipple 3 with a force greater
than the retaining force in needle holder 2 given the undeformability
of the former and the greater roughness of its surface, which is
also provided with longitudinal grooves for the complete expulsion
of liquids in the final stage, although these grooves may belong
to the nipple of the needle.
In FIG. 3 excess pressure has been applied to the piston, which
causes final advance of front end 12 further compressing elastomer
washer 11 and not capturing end 9 which has encountered a stop
in its travel. For this reason, elastic tongues 13 of inner tube
8 break off perimetral projection 14 of capturing unit 9 leaving
this exposed to the pull of elastic medium 15 which being anchored
at the rear to plug 16 causes it to be retracted with the captured
needle, while the air between them, which might impede rearward
movement, escapes through orifice or orifices 17. The needle holder
guide is sufficient to ensure that the needle is retracted linearly
while it is present in the exterior, while absorbent member 18 cleans
it avoiding any dripping of residual liquids. In the illustrations,
it can be seen that the piston has a leak tight sliding head 19
and a posterior section of reduced cross section in order to reduce
friction giving rise to a peripheral space 20 for the escape of
air. In addition to this, the syringe illustrated in the example
is equipped with a stop 21 in the interior of its outer tube, which
when in contact with perimetral step 22 on the piston prevents it
from any subsequent excursion when at its maximum extension.
FIG. 4 shows a needle holder 2 with its needle 1 fitted and a protective
cap over the front opening of the syringe, in which can be seen
elastic tongues 6 and its posterior stop step 5.
FIG. 5 is intended to show a posterior elastic tongue 23 in a needle
holder 2 which is complementary but not essential, which is designed
to retain coupling nipple 3 of needle 1.
In FIG. 6 needle holder 2 forms an integral part of extension
tube 4 and belongs to a syringe with a nonretractable internal needle
equipped with a protective cap.
Finally, FIGS. 7 8 9 10 and 11 show in diagrammatical form various
alternative cross sections of syringes which are capable of operating
using the basic principle described, selected from a large possible
variety. The first of these shows a cylindrical syringe with a concentric
needle; the next is a cylindrical syringe with the center of the
needle displaced and a longitudinal guide 24 which prevents the
piston from rotating with respect to the outer tube, given that
correcting guide 25 in the capturing plug prevents it from being
displaced angularly with respect to the piston; in FIG. 9 the cross
section of the syringe describes an ellipse and the axis of the
needle is central, for which reason it is self-centering. The following
FIG. 10 shows a cross section like the former but its needle is
eccentric, so that it does not need any longitudinal guide, provided
that it has first been correctly assembled, and the final FIG. 11
shows a cross section of an anatomical syringe which is ideal for
use almost parallel to the body surface, with its concave side supported
on it to avoid lateral movements, this conformation also being self-centering.
Modifications may in practice be incorporated in the disposable
syringe with an automatically retractable hypodermic needle as described
and illustrated by examples which modifications must be regarded
as variant embodiments lying within the scope of the protection
of this patent of invention which is described in its essentials
by the text of the clauses of the following claims.
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