Safety syringe abstract
A disposable safety syringe with a hypodermic needle of a type
comprising a syringe body inside which a plunger is guided for sliding
movement and wherein said needle is guided for movement to an away
position inside the syringe body, further comprises: an engagement
peg formed at the plunger end integrally therewith; a holding pad
for said needle arranged to be movable within said body and provided
with a seat for engagement with the peg; and an elastically yielding
seal having a non-uniform thickness and being attached to the plunger
end. The needle, as caught up after injection by the plunger peg
engaging in a corresponding seat on the pad, is fully retracted
into the syringe body and subjected to a sideways push from the
seal effective to offset it and make re-use of the syringe impossible.
Safety syringe claims
I claim:
1. A disposable safety syringe, comprising:
a syringe body;
a plunger engageable with said body for sliding movement within
said body;
a hypodermic needle having an extended position outside said body
and a retracted position within said body;
an engagement peg formed at one end of said plunger;
a supporting pad, for supporting said needle, arranged within said
body for axial movement within said body, said pad having an engagement
seat formed therein for engagement with said peg; and
an elastically yielding seal mounted to said one end of said plunger;
wherein said elastically yielding seal applies an elastic pressure
to said needle when said needle is retracted into said body for
biasing the needle out of alignment with the longitudinal axis of
the needle when the needle is in an extended position.
2. A syringe according to claim 1 wherein said peg is provided
with a substantially mushroom-shaped head.
3. A syringe according to claim 1 wherein said seal is mounted
to said one end of said plunger at a location inboard relative to
said peg.
4. A syringe according to claim 1 wherein a portion of said seal
slopes gently away from said one end of said plunger such that said
seal is provided with a non-uniform thickness.
5. A syringe according to claim 1 wherein said seal is mounted
to an exterior surface of said one end of said plunger.
6. A syringe according to claim 1 wherein said peg is integrally
formed with said one end of said plunger.
7. A disposable safety syringe, comprising:
an elongate syringe body;
a plunger engageable with said body for sliding movement within
said body;
a hypodermic needle having an extended position outside said body
and a retracted position within said body;
an engagement peg integrally formed with and extending from one
end of said plunger;
a supporting pad, for supporting said needle arranged within said
body for axial movement within said body, said pad having an engagement
seat formed therein for engagement with said peg; and
an elastically yielding seal mounted to an exterior surface of
said one end of said plunger, said seal having a portion that slopes
gently away from said end of said plunger such that said seal has
a nonuniform thickness;
wherein said elastically yielding seal applies an elastic pressure
to said needle offset from the longitudinal axis of the syringe
body for biasing the needle out of alignment with said axis when
said peg engages said engagement seat and said needle is retracted
into said body.
Safety syringe description
DESCRIPTION
This invention relates to a disposable safety syringe with a hypodermic
needle, of a type which comprises a syringe body inside which a
plunger is guided for sliding movement, said needle being guided
for movement to an away position within the syringe body.
It is a well-known fact that disposable syringes of the above type
are usually formed from a non-toxic synthetic plastics material,
and comprise:
a tubular syringe body having a conically tapering end into a tip
defining a small diameter bore;
a hypodermic needle having its remote end from its needle point
end fitted over said conical end of the syringe body;
a plunger consisting of a rod fitted removably into the syringe
body and being guided within that body for sliding movement therethrough;
a rubber seal attached to the plunger end fitted into the syringe
body and having a slightly larger outside diameter than the inside
diameter of that body to provide a tight fit for the plunger; and
a protective cap for the hypodermic needle.
These five elements constitute the basic components of any disposable
syringes currently available on the market, each syringe being merchandised
in a respective sealed package on which the manufacturer merely
shows a warning to the effect that the syringe is to be used once.
It is a known fact, however, that such syringes are usually left
after use mostly anywhere, especially by drug addicts, thereby endangering
the health of the community, and children's especially, being carriers
of such infections as hepatitis or AIDS.
To prevent such a potential danger, the prior art has proposed
the use of a particular syringe type, as described in U.S. Pat.
No. 4702738.
That patent discloses a syringe comprising a tubular case fitting
slidably over the exterior of the syringe body to cover the needle
for protection before and after use.
The syringe body is formed with guide flutes for that case, and
has toothed means of engagement to lock the case in a position where
it would cover the needle.
This prior approach has, first and foremost, the drawback that
an additional part is required in the syringe construction, which
affects production cost adversely. Furthermore, the case makes for
a less easily handled syringe in use, while the provision of the
flutes and locking means on the syringe body adds, in turn, to the
production costs.
A second prior approach is described instead in U.S. Pat. No. 4507117
which discloses a syringe wherein the needle is mounted to a slider
movable axially through the interior of the syringe body and equipped
with hooking means for engagement with the body bottom to provide
a working setting with the needle extended from the body.
The syringe plunger is in turn provided with hooking means whereby
the needle slider can be engaged and, on completion of an injection
cycle, withdrawn into the syringe body.
The hooking means are releasable catches of the bayonet type which
require for their operation rotational movements of both the plunger
and the needle-holding slider.
This second approach has, however, a serious drawback in that the
needle and its holding slider are normally housed within the syringe
body, and requires to be preliminarly pushed into the working position
by means of the plunger which, after the slider is anchored on the
bottom wall of the syringe body, must be released and driven backwards
into its working position.
This, additionally to creating problems during the syringe assembling
stage and in the use thereof, impairs the disposable feature of
the syringe because the needle, although retractable, may be pushed
once again to its working position.
A further prior art approach is described in U.S. Pat. No. 4767413
which discloses a syringe for dental use including means for automatically
retracting the needle into the syringe body. However, this prior
syringe has so many component parts as to be an unduly complicated
construction unsuitable for the very large volume manufacturing
methods employed with syringes of the disposable type.
Further, not even the latter syringe design can prevent re-use.
The problem underlying this invention is to provide a novel type
of disposable safety syringe which has constructional and performance
characteristics of great simplicity, such that once it has been
used and its needle retracted into the syringe body, there is no
way of re-using the same syringe twice, thereby overcoming the noted
drawbacks with which the prior art is beset.
This problem is solved by a syringe of the type specified above
comprising:
an engagement peg formed at the plunger end integrally therewith;
a supporting pad for said needle arranged to be movable axially
within said body, in said pad there being formed an engagement seat
for said peg; and
an elastically yielding seal mounted to the plunger end to apply
an elastic pressure offset from the needle axis and tending to bring
the needle out of alignment once the needle has been retracted into
said body.
The features and advantages of the syringe according to the invention
will become apparent from the following detailed description of
an embodiment thereof, to be taken by way of example and not of
limitation in conjunction with the accompanying drawings.
In the drawings:
FIG. 1 is a schematical view showing the syringe of this invention
in longitudinal section;
FIG. 2 is a schematical view showing a variation of the syringe
shown in FIG. 1 also in longitudinal section;
FIGS. 3 to 7 are respective schematical detail views of the syringe
shown in FIG. 2;
FIG. 8 is a longitudinal section view showing schematically a second
variation of the syringe of FIG. 1;
FIGS. 9 and 10 are respective detail views of the syringe shown
in FIG. 8;
FIG. 11 is a longitudinal section view showing schematically a
further variation of the syringe of FIG. 1; and
FIGS. 12 to 14 are respective detail views of the syringe shown
in FIG. 11.
With reference to the drawing views, generally and schematically
shown at 1 is a disposable apyrogenous syringe according to the
invention.
The syringe 1 comprises a syringe body 2 made of a clear synthetic
plastics material and having a tubular shape open at one end and
tapering at the opposite end with a bottom wall 23 formed centrally
with a bore 24. Through that bore 24 there is passed and guided
for sliding movement a hypodermic needle 10 which is carried on
a pad 29 fitting inside the body 2.
The syringe 1 also comprises a plunger or piston 13 slidably within
the body 2.
Advantageously, an engagement peg 27 is provided which has an substantially
mushroom-shaped head 32 and is a unitary construction with the plunger
end 28 inside the body 2; in addition, said pad 29 is formed with
an engagement seat 30 for receiving said peg 27.
Mounted to the end 28 of the plunger 13 is a seal 27 which is elastically
yielding in nature and has a non-uniform thickness. More specifically,
it includes a portion 31 of increased thickness which defines a
surface arranged to slope slightly toward the pad 29.
The syringe of this invention operates as described herein below.
After the liquid to be injected has been drawn in and the injection
cycle completed, the end 28 of the plunger 13 and specifically
the peg 27 thereon, is engaged with the pad 29 by applying a slight
pressure on the plunger and, concurrently therewith, compressing
the seal 15 elastically.
The needle is drawn manually away by moving the plunger 13 backwards
to where the needle frees itself from the guide provided by the
bore 24.
The thicker portion 31 of the seal 15 will exert on the pad 29
a pressure force which is directed laterally of and offset from
the needle own axis on account of its higher elastic deformation.
As a result, the needle 10 is brought out of alignment, thereby
it cannot be re-inserted through the bore 24 and permit re-use of
the syringe.
With particular reference to the example shown in FIG. 8 a variation
of the inventive syringe will be now described. In this variation,
cooperating items and parts which have the same construction as
and operate similarly to the preceding embodiment are denoted by
similar reference numerals.
In this variation, the hypodermic needle 10 is mounted to substantially
form an extension of an axially hollow rod 4 which has a head 33
next to the needle provided with a seal 20. The head 33 is formed
with a seat 17 for receiving an engagement peg 37 affixed centrally
to the end 28 of the plunger 13.
That peg 37 is formed centrally on a member 16 connected to the
end 28 via a rubber seal 15.
A safety device mounted externally of the body 2 end adjacent to
the needle 10 is also provided. This device 18 is essentially a
crescent-shaped shutter plate being journalled outside the bottom
wall 23 of the body 2 and constantly biased by a spring 19 toward
a position where it would block the bore 24 through which the needle
10 is arranged to pass.
The operation of the syringe according to this variation is substantially
similar to that of the embodiment previously discussed in that the
needle is withdrawn into the syringe body manually by retracting
the plunger 13.
Once the rod 4 has been slipped off the guide formed by the bore
24 the shutter 18 being no longer constrained by the presence
of the rod 4 will be automatically shifted to a position blocking
the bore 24 by the elastic bias force from the spring 19 thereby
making the syringe impossible to re-use.
It is further contemplated that the seal 15 connecting the member
16 to the end 18 has yielding properties selected to defeat any
attempt at forcibly pulling the needle out of the syringe.
A second variation of the syringe according to the invention is
shown in FIG. 2.
In this variation, a coil spring 3 is provided inside the body
2 which has predetermined rate and calibration.
The hypodermic needle 10 is mounted to be an extension of the axially
hollow rod 4 which has its head 33 next to the needle provided
with a peripherally tight-fitting seal 5. Also provided is a yielding
means to hold said spring 3 in a pre-compressed state.
Above the seal 5 there is mounted a centrally bored expansible
washer 6 the outside diameter whereof is slightly less than the
inside diameter of the body 2.
Provided on the interior of the body 2 is a groove 14 extending
radially to the syringe axis and being located at a predetermined
height, indicated at X.
The spring 3 is first wound around the rod coaxially therewith
and then inserted into the body 2 to lie between the bottom wall
23 and the head 33 of the rod 4. That spring is compressed until
the washer 6 registers with the groove 14.
A conically shaped spreader member 7 formed in turn with a central
bore 36 is inserted into the central bore 34 of the washer 6 such
that the latter can fit on expanding into the groove 14 and hold
the spring 3 in a pre-compressed state.
In this variation, the end 28 of the plunger 13 mounts a conventional
seal 8 and provided at the open rear end of the body 2 is a plate-like
stop 9 effective to prevent the plunger from slipping fully off
the body 2.
In addition, a pin 35 is affixed centrally to the plunger end and
effective to intercept the spreader member 7.
The reference numeral 11 denotes a safety device mounted externally
of the body 2 end adjacent to the needle 10. This device is essentially
a crescent-shaped shutter plate journalled on the exterior of the
bottom wall 23 of the body 2 and constantly biased by a spring 12
toward a position where it blocks the bore 24 through which the
needle 10 is passed.
The operation of a syringe according to this variation is described
herein below, with the assumption that a liquid to be injected has
been first drawn into conventionally by operation of the plunger
13.
On completion of the injection cycle, by applying a certain pressure
force on the plunger 13 the pin 35 is caused to act on the member
7 and release the washer 6.
On the plunger being pushed fully down, the member 7 will be made
to drop in the rod 4 and release the washer 6 which is thus restored
to its original diameter.
As a result, the pre-compressed spring 3 being no longer constrained,
will be allowed to expand and automatically push the rod 4 and needle
10 upwards until the latter becomes fully retracted inside the body
2.
Concurrently therewith, the shutter 11 being no longer constrained
by the presence of the rod 4 will be automatically shifted to block
the bore 24 by the elastic bias from the spring 12.
A further variation will be now described with reference to FIG.
11.
In this variation, a discrete means is provided for holding the
spring 3 pre-compressed inside the body 2.
In particular, the needle 10 is mounted on a holding slider 21
provided peripherally with a seal 5. The spring 3 is inserted in
a pre-compressed state between the bottom wall 23 of the body 2
and that slider 21. In this connection, there are provided a substantially
C-shaped spring washer 26 and a small ball 25 having a larger diameter
than the inside diameter of the washer 26.
The ball 25 is forced into the central portion of the washer which,
on expanding, will lock securely against the inner walls of the
body 2 at the height indicated at X.
Similarly to the example previously described, a pin 35 is provided
on the end 28 of the plunger 13 and adapted to intercept, as the
plunger is completing its stroke, the ball 25 and push it into a
seat 37 formed on the slider 21 at the needle 10 inlet, thus releasing
the washer 26.
For completeness of illustration, it should be noted that the bottom
wall 23 of the body 2 consists of an interfitted end cap formed
with the calibrated bore 24 through the center whereof the hypodermic
needle 10 is made to pass.
That end cap 38 is provided for those instances where the parts
making up the syringe of this invention ought to be assembled and
installed with a simplified and/or more convenient procedure.
In addition, a stop 22 is provided which consists of a C-like retaining
ring fitted into a groove at the open rear end of the body 2. That
stop 22 is effective to prevent the plunger 13 from slipping out
of the syringe body.
On the pin 35 intercepting the ball 25 and releasing the washer
26 the latter will resume its original diameter, which is somewhat
less than the inside diameter of the body 2 thus allowing the pre-compressed
spring 3 to expand.
This expansion movement of the spring 3 will drive the slider 21
in a guided fashion away from the bottom wall 23 of the body 2
to automatically retract the needle 10 inside the body 2 and out
of the calibrated bore 24.
Once taken out of the guiding bore 24 the needle 10 will be moved
out of alignment by the elastic flexibility of the rubber seal 5
which is unable to hold the needle point aligned. As a result, should
an attempt be made to push the needle out by means of the plunger,
it would trip on the syringe bottom and bend.
In any case, it would be impossible to re-use the syringe also
because, once the spring 3 is released, the plunger end would remain
at all times in contact with the slider 21 and hinder accordingly
sucking in any liquids.
The syringe of this invention has a major advantage in that it
comprises a peculiarly low number of component parts, and may be
manufactured in large and very large volumes on the same automated
assembling equipment as currently used by most manufacturers.
In addition, a syringe according to this invention does provide
single use capabilities by ensuring irreversible retraction of the
needle into the syringe body. |