Safety syringe abstract
A hypodermic safety syringe assembly (10) includes a cylindrical
barrel (12) having a front end defining a first aperature (14) and
a rear end defining a second aperature (16), a closure member (32)
shaped to engage the barrel (12) at or adjacent the front end thereof
to seal the first aperature (14), and a piston assembly (18) reciprocally
movable within the barrel (12) and includes a retractor (20) terminating
in a piston formation (24) engageable with the closure member (32)
to disengage the closure member from the front end of the barrel
so that a hypodermic needle (40) attached thereto can be withdrawn
into the barrel (12) after use, wherein the closure member (32)
includes a barrel engaging formation (4448) releasably engageable
within a closure member engaging formation (64) at the front end
of the barrel (12), and a piston coupling formation (5054) for
engaging a closure member coupling formation (6869) on the piston
(24), with inter-engagement of the piston and closure member coupling
formations (5054;6869) being arranged to facilitate disengagement
of the barrel engaging and closure member engaging formations (64;
4448) from one another and to allow withdrawal of the piston assembly
(2024), closure member (32) and hypodermic needle (40) into the
barrel (12).
Safety syringe claims
1. A hypodermic safety syringe assembly including a cylindrical
barrel having a front end defining a first aperture and a rear end
defining a second aperture, a closure member shaped to engage the
barrel at or adjacent the front end thereof to seal the first aperture,
and a piston assembly reciprocally movable within the barrel and
including a retractor terminating in a piston formation engageable
with the closure member to disengage the closure member from the
front end of the barrel so that a hypodermic needle attached thereto
can be withdrawn into the barrel after use, wherein the closure
member includes a barrel engaging formation releasably engageable
within a closure member engaging formation at the front end of the
barrel, and a piston coupling formation for engaging a closure member
coupling formation on the piston, with inter-engagement of the piston
and closure member coupling formations being arranged to facilitate
disengagement of the barrel engaging and closure member engaging
formations from one another and to allow withdrawal of the piston
assembly, closure member and hypodermic needle into the barrel.
2. The assembly of claim 1 wherein the closure member includes
an inner skirt portion connected to an outer skirt portion by a
hinge, with a displacement groove located between the inner and
outer skirt portions.
3. The assembly of claim 2 wherein the barrel engaging formation
includes a lip extending from the outer skirt portion, and the closure
member engaging formation includes a lip receiving recess adjacent
the front end of the barrel.
4. The assembly of claim 3 wherein the piston coupling formation
includes at least one first projection and a corresponding projection
receiving recess located radially outwardly of the first projection,
and the closure member coupling formation includes a second projection
and a corresponding recess located radially inwardly of the second
projection, with the second projection being arranged to displace
the first projection inwardly about the hinge during inter-engagement
of the piston coupling formation and closure member coupling formation
so as to urge the outer skirt formation, from which the first projection
depends, inwardly so as to disengage the lip from the lip receiving
recess.
5. The assembly of claim 4 wherein the first projection is a first
annular lobe formation and the second projection is a second annular
lobe formation.
6. The assembly of any one of the above claims including detaining
means for detaining the used needle in a locked safe position within
the barrel.
Safety syringe description
BACKGROUND OF THE INVENTION
[0001] This invention relates to a hypodermic safety syringe assembly.
[0002] The needles of used hypodermic syringes pose an increasing
threat of the transmissibility of potentially lethal infections
such as HIV.sup.+ and hepatitis B viruses, not only to persons administering
the injection, but also to persons who are charged with handling
such equipment immediately after use, to others who are exposed
to the possibility of accidental, post-injection contact in environments
in which hypodermic procedures are routinely administered, and to
still others who might come into contact with used syringes which
have been inadequately disposed of.
[0003] Various safety hypodermic syringes have been designed which
attempt to minimise these risks. These include various forms of
needle containment and needle disposal units which respectively
seek to encapsulate a used needle or allow such used needle to be
destroyed by incineration or the like. In order to be effective,
needle destroying devices have to be available in situ at all locations
where such procedures are undertaken. The effectiveness of needle
destroying devices is further reduced by the fact that the sharp
end of the used needle may typically be exposed for an appreciable
period of time before it is destroyed.
[0004] Another arrangement which is available comprises a cylindrical
sleeve which fits around the barrel of a syringe, and which can
be extended forward over the needle attached to the syringe after
use. When the sleeve is fully extended, locking formations on the
sleeve engage complemental locking formations formed on or adjacent
the end of the syringe barrel so that the sleeve cannot be retracted.
[0005] Drawbacks of protective sleeve arrangements include the
fact that in a number of such devices the shield has an open end,
which is large enough to allow a user's finger to enter and to contact
the needle. A directly concomitant disadvantage is the fact that
in order to obviate this danger, the needle used has to be substantially
shorter than the length of the syringe barrel and shield. The extended
and locked syringe/sleeve assembly is relatively long and bulky,
and uses a substantial additional mass of plastic material compared
with the syringe alone. Arrangements of this type are also relatively
complicated to manufacture, frequently involving a complete re-engineering
of the syringe in order for it to co-operate in secure locking engagement
with the sleeve. Examples are provided by the disclosures in U.S.
Pat. Nos. 5053018 and 5304149 both of which teach a hypodermic
syringe and needle assembly on which is mounted a shield which is
movable between a retracted position in which the needle point is
exposed and an extended position in which the needle point is covered.
[0006] User resistance has been encountered to the added bulk and
overall diameter of the assembly contributed by the sleeve, which
is particularly disadvantageous when the needle point needs to be
acutely tangential to the surface of the skin of the patient. The
fact that the contents and the graduations on the syringe must be
viewed through the material of the shield has also proved inconvenient
and can lead to errors in use.
[0007] An alternative arrangement where the syringe is substantially
re-engineered typically proposes a device having a barrel, sheath
and piston, the piston being provided with a liquid passageway interconnectable
with the barrel. The injection of fluid is accomplished by moving
the barrel relative to the sheath (as opposed to the more familiar
approach of moving the piston relative to the barrel, in conventional
hypodermic syringe assemblies). An example of this approach is provided
by South African Patent 93/5302 which teaches the automatic and
non-discretionary single use safe rendition of a needle.
[0008] Three disadvantages of this approach have manifested themselves
in practice. The first is the fact that the procedure represents
a significant departure from the operation of a conventional syringe.
Nursing staff have shown resistance to the required adjustment from
what is a comfortable and familiar routine. A further disadvantage
is the fact that this approach requires a large number of component
parts, which adds significantly to the cost of both the moulds and
mould operations required and of the materials used. A final disadvantage
is the impression left with the practitioner that the precise point
when the device is rendered needle-safe is no longer a matter of
professional choice, but is rather a matter of when the manufacturer
has prescribed that it is advisable or necessary.
[0009] The highest incidence of the HIV.sup.+ and hepatitis viruses
generally occur in poor, third world countries which can ill afford
devices reliant on significant re-engineering, which do not take
into account the high level of the capital invested world-wide in
manufacturing facilities for and stocks of conventional hypodermic
syringes and needles.
[0010] It is an object of the invention to provide an alternative
safety syringe assembly which allows for an administering procedure
which does not depart significantly from that of a conventional
syringe, and which does not utilise an additional outer sheath or
shield.
SUMMARY OF THE INVENTION
[0011] According to a first aspect of the invention there is provided
a hypodermic safety syringe assembly including a cylindrical barrel
having a front end defining a first aperture and a rear end defining
a second aperture, a closure member shaped to engage the barrel
at or adjacent the front end thereof to seal the first aperture,
and a piston assembly reciprocally movable within the barrel and
including a retractor terminating in a piston formation engageable
with the closure member to disengage the closure member from the
front end of the barrel so that a hypodermic needle attached thereto
can be withdrawn into the barrel after use, wherein the closure
member includes a barrel engaging formation releasably engageable
within a closure member engaging formation at the front end of the
barrel, and a piston coupling formation for engaging a closure member
coupling formation on the piston, with inter-engagement of the piston
and closure member coupling formations being arranged to facilitate
disengagement of the barrel engaging and closure member engaging
formations from one another and to allow withdrawal of the piston
assembly, closure member and hypodermic needle into the barrel.
[0012] The closure member preferably includes an inner skirt portion
connected to an outer skirt portion by a hinge, with a displacement
groove located between the inner and outer skirt portions.
[0013] The barrel engaging formation preferably includes a lip
extending from the outer skirt portion, and the closure member engaging
formation preferably includes a lip receiving recess adjacent the
front end of the barrel.
[0014] The piston coupling formation preferably includes at least
one first projection and a corresponding projection receiving recess
located radially outwardly of the first projection, and the closure
member coupling formation preferably includes a second projection
and a corresponding recess located radially inwardly of the second
projection, with the second projection being arranged to displace
the first projection inwardly about the hinge during inter-engagement
of the piston coupling formation and closure member coupling formation
so as to urge the outer skirt formation, from which the first projection
depends, inwardly so as to disengage the lip from the lip receiving
recess.
[0015] The first projection is preferably a first annular lobe
formation and the second projection is preferably a second annular
lobe formation.
[0016] The assembly preferably includes detaining means for detaining
the used needle in a locked safe position within the barrel.
[0017] An embodiment of the invention is described in detail in
the following passages of the specification which refer to the accompanying
drawings. The drawings, however, are merely illustrative of how
the invention might be put into effect, so that the specific form
and arrangement of the features shown is not to be understood as
limiting on the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 shows a partly cross-sectioned side view of a safety
syringe assembly according to the invention;
[0019] FIG. 2A shows an underplan view of a closure member forming
part of the safety syringe assembly of FIG. 1;
[0020] FIG. 2B shows a cross-sectional side view along the line
2B-2B of FIG. 2A;
[0021] FIGS. 3A to 3C show cross-sectional detailed side views
of the manner in which the closure member engages the front end
of the barrel during assembly of the safety syringe assembly of
the invention;
[0022] FIGS. 3D to 3H show, stepwise, the procedure involved in
the piston formation engaging with and retracting the closure member
into the barrel of the safety syringe assembly;
[0023] FIG. 4 shows a partly cross-sectioned side detailed view
of the piston formation and closure member in a retracted engaged
position; and
[0024] FIG. 5 shows a partly cross-sectioned side view of the safety
syringe in the retracted engaged position.
DETAILED DESCRIPTION OF THE DRAWINGS
[0025] Referring first to FIG. 1 safety syringe assembly 10 of
the invention comprises a barrel 12 having a front opening 14 and
a rear opening 16. A piston assembly 18 is arranged to travel reciprocally
within the barrel 12 and includes an elongate retractor 20 having
a cruciform profile terminating in a rear finger disc 22. A piston
formation 24 extends from the front end of the retractor, and includes
front and rear piston discs 26 and 28 and an O-ring 30 located within
an intervening annular recess 31. The front piston disc 26 is coupled
to a closure member 32 formed with a central spigot formation 34
extending from a skirt 36. A needle hub 38 fits over the needle
spigot 34 in a snug friction fit, and a needle 40 extends from the
needle hub 38.
[0026] Referring now to FIGS. 2A and 2B, the skirt 36 of the closure
member 32 includes a rigid inner skirt portion 42 and an outer peripheral
relatively flexible skirt portion 44 which is arranged to flex about
a narrowed neck portion defining a radially hooped hinge 46. The
outer peripheral flexible skirt portion 44 terminates in a barrel-engaging
lip 48. A series of piston-engaging lobes 50 extend axially inwardly
and radially outwardly from the back of the flexible skirt portion
44. The lobes 50 are arranged in an annulus, with a total of 24
lobes being defined by evenly spaced gaps 52 therebetween which
are designed to reduce hoop stress and facilitate inward flexure
of the flexible skirt portion 44. A piston-receiving recess 54 is
defined between the free ends of the lobes 50 and the lip 48 of
the flexible skirt. There is a displacement groove 74 between the
inner skirt portion 42 and outer skirt portion 44.
[0027] Referring now to FIGS. 3A to 3C, the syringe barrel 12 terminates
in an inwardly extending flange 56 and defines a round cylindrical
inner surface 58 which extends for almost the entire length thereof.
A ramp 60 extends between the cylindrical surface 58 and a reduced
diameter land 62 and a lip-locating recess or groove 64 is located
between the land 62 and the flange 56. The closure member 32 is
fitted to the syringe barrel by inserting it through the rear opening
16 thereof. As the closure member 32 travels down the barrel, the
flexible skirt portion 44 is marginally flexed inwardly as the lip
48 contacts the inner surface 58 of the barrel. As the lip 48 rides
up the ramp 60 and onto the reduced diameter land 62 the outer
flexible skirt portion 44 flexes inwardly in the direction of arrow
65 about the hinge 46 as is clear from FIG. 3B. Further forward
movement of the closure member 32 causes the barrel-engaging lip
48 to locate firmly within the lip receiving recess 64 at the front
end of the barrel, with the outer skirt portion 44 being in a partly
inwardly flexed position.
[0028] When the closure member 32 is in the forward engaged position
of FIG. 3C, a pushing force in the direction of arrow 67A translates
into an outwardly pivoting movement of the outer flexible skirt
portion 44 in the direction of arrow 67B. This has the effect of
expanding the outer diameter of the skirt portion and jamming the
lip 48 of the skirt even more tightly within the detent or recess
64.
[0029] After administration of the injection, the piston formation
24 is moved forwards within the barrel 12 to the position indicated
in FIG. 3D. The front piston disc 26 is formed with an outer closure
member-engaging lobe 68 and an adjacent lobe-receiving recess 69
for receiving the lobe 50 of the closure member 32. As the piston
formation 24 advances to the FIG. 3E position, an outer peripheral
rib formation 70 bears firmly against the ramp 60. As the outer
diameter of the rib 70 is greater than the progressively decreasing
inner diameter of the ramp 60 this results in the relatively rigid
front piston disc 26 beginning to outwardly deform the syringe barrel
12 as is indicated by bulge 72. The barrel 12 is typically formed
from a softer grade of polypropylene than the piston formation to
facilitate the outward deformation of the barrel walls.
[0030] In the FIG. 3E position, the geometry of the arrangement
is such that the outermost points of the first piston-engaging lobes
50 and the second annular closure member-engaging lobe 68 are tangential.
Further advancement of the piston formation induces a complex combination
of forces which ultimately result in the first set of lobes 50 rotating
inwardly about the hinge 46 in the direction of the arrow in the
displacement groove 74. The displacement groove 74 permits inward
rotation of the first set of lobes 50.
[0031] In the engaged position of FIG. 3G, the piston formation
24 and the closure member 32 are fully inter-engaged, with the second
annular lobe 68 nesting within the recess 54 defined between the
lobe 50 and the outer lip 48 and the first set of lobes 50 nesting
within the annular recess 69 defined within the front piston disc
26. In this position, further outward deformation of the barrel
occurs at 76. The extent of deformation can clearly be seen in FIG.
3F, where the degree of overlap between the front piston disc 26
and the non-deformed barrel wall 12 is shown at 78. The radially
inward movement of the lobe 50 results in the lip 48 being disengaged
from the recess 64 and a clearance gap 80 being defined. As is clear
from FIG. 3H, the now coupled piston assembly 18 and closure member
32 can be retracted by virtue of the simultaneous inter-engagement
of the lobes 50 and 68 and the disengagement of the lip 48 from
the recess 64.
[0032] The piston assembly 18 closure member 32 and needle hub
assembly including the used needle 40 and the needle hub 38 are
subsequently retracted fully to the FIGS. 4 and 5 position in which
the used needle point is locked safely within the syringe barrel,
with the narrow diameter opening 14 constituting a finger barrier.
It can clearly be seen how the inner surface of the barrel wall
12 has been profiled with a piston formation and closure member-detaining
land 82 being defined between a front rib or detent 84 and a rear
rib or detent 86 of reduced diameter, with the rear rib 86 being
sufficiently prominent to prevent both the rear and front piston
discs 28 and 26 respectively from being retracted out of the barrel.
The lip 48 of the outer skirt portion is located just behind the
rib 84 which detains it in the fully retracted position, and prevents
subsequent forward movement of the inter-engaged piston formation
and closure member which carries the needle hub and used needle
40. A frangible connection 88 is provided between the rear piston
disc 28 and the retractor 20. The frangible connection 88 has been
designed so that it has both tensile and compressive strength in
an axial direction, but is weak in the shear vector which allows
the retractor to be broken off in the manner illustrated. Both the
retractor and the syringe barrel safely housing the used needle
can now be disposed of. |