A disposable syringe having a needle which may be easily withdrawn
to safety after use is disclosed. The syringe includes a cylinder
and plunger in which a threaded extension or threadlock on the forward
end of the plunger is capable of engaging a threadbore element positioned
within the forward neck portion of the cylinder after the injectable
fluid has been expelled from the cylinder. The threadbore element
is secured to the needle. Rotation of the plunger causes the threadlock
to engage the threadbore and the needle may be withdrawn into the
interior of the cylinder by pulling the plunger rearwardly.
What is claimed and desired to be secured by Letters Patent is:
1. A disposable syringe device having a retractable needle, comprising:
a cylinder member having a neck portion at one end thereof; a plunger
mounted for reciprocal movement within said cylinder, said plunger
having a threaded portion at one end; a threadbore member mounted
within said neck portion in fluid tight engagement therewith, said
threadbore member having an inner bore with a threaded portion in
said bore for receiving the threaded portion of said plunger; a
tapered post member mounted on one end of said threadbore member
outwardly of said cylinder, said post member having said needle
mounted therein; and a gasket mounted about the circumference of
said threadbore member to provide fluid tight engagement between
the threadbore member and the neck portion of said cylinder.
2. The syringe device of claim 1 wherein said plunger has a piston
member mounted on the threaded end portion of said plunger.
3. The syringe device of claim 1 wherein said threadbore member
has a tapered hub portion on one end for receiving said post member.
4. The syringe device of claim 1 wherein said gasket is of a size
and material so as to allow the threaded end portion of said plunger
to press against and engage the threadbore upon forward movement
of said plunger without having the gasket pass through the cylinder
neck portion and wherein the threadbore member with attached gasket
may be withdrawn through said cylinder neck upon rearward movement
of said plunger.
5. The syringe device of claim 5 wherein the cylinder neck has
a rolled forward edge producing a slightly smaller diameter at the
extreme forward end of the cylinder neck to prevent forward movement
of the gasket.
6. The syringe device of claim 2 wherein said threaded end portion
of the plunger is of reduced diameter relative to the piston member.
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to a disposable syringe device having
a retractable needle or cannula. More particularly, the present
invention relates to a disposable syringe which allows the needle
to be retracted, once it has been used, to a position of safety
so as to prevent personal contact with the needle tip.
The viral disease AIDS has become of great concern to health professionals
because of its obvious potentially devastating impact on the health
and monetary resources of this country. To date, the only "cure"
which amounts to control, is through prevention of the spread of
this uniformly fatal disease. The newest high-risk group is health
Not only do known AIDS patients represent a source for the spread
of disease among health care workers but so does the general population.
There are large groups of people who have been exposed as intravenous
drug users, people who have received blood transfusions during a
certain period of time when there was no testing, and people who
have been infected with the virus through sexual contact.
Health care workers, in addition, may be exposed within the hospital
environment by contact with body secretions but, in particular,
through accidental needle punctures.
Commercially available disposable syringes have certain generic
characteristics and components which are used industry-wide. Indeed,
many of these parts are interchangeable from manufacturer to manufacturer.
Previous syringe devices are described in the following U.S. patents:
U.S. Pat. No. 4026287 to Haller; U.S. Pat. No. 4507117 to Vining
et al.; U.S. Pat. No. 4650468 to Jennings; U.S. Pat. No. 4675005
to DeLuccia; U.S. Pat. No. 4710170 to Haber et al.; U.S. Pat.
No. 4747830 to Gloyer et al.; U.S. Pat. No. 4770655 to Haber
et al.; U.S. Pat. No. 4790822 to Haining; U.S. Pat. No. 4801295
to Spencer; U.S. Pat. No. 4804370 to Haber et al.; and U.S. Pat.
No. 4808169 to Haber et al.
By the present invention, there is provided an improved syringe
having a unique mechanism which allows the exposed needle after
use to be easily withdrawn to safety within the syringe without
the need for breakage of any portion of the device. Use of the syringe
of the present invention virtually eliminates the potential for
the health care worker to be stuck by an infected needle.
The present syringe has a threaded extension or threadlock at the
forward end of the plunger which replaces the strut of the generic
model. The threadlock passes through a fluid-tight threadport extending
axially through the center of the rubber piston. In the post injection
state the plunger threadlock has entered a threadbore element which
is secured to the needle. The threadlock and threadbore may be easily
engaged by a simple clockwise turn of the plunger. Upon engagement
of the threadlock with the threadbore, the entire threadbore assembly,
including gasket, hub and ultimately the needle, may be withdrawn
safely into the syringe cylinder. At the base of the syringe cylinder,
stop elements are positioned to prevent the plunger assembly from
being removed from the back side of the syringe, further protecting
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded perspective view of the syringe device of
the present invention.
FIG. 2 is a cross sectional view of the syringe device of FIG.
1 showing the piston as positioned for movement axially within the
FIG. 3 is a cross sectional view of the syringe device of FIG.
1 showing the threadlock of the plunger engaged with the threadbore.
FIG. 4 is cross sectional view of the syringe device of FIG. 1
showing the needle or cannula withdrawn within the cylinder.
FIGS. 5 through 7 are perspective views of the syringe device of
FIG. 1 in various stages of operation.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the embodiment of the invention as shown in FIGS. 1 through
7 there is provided a syringe device 10 in which a plunger 12 with
removably attached piston 14 is positioned for axial movement within
a cylinder or barrel 16. The cylinder 16 is generally of a clear
plastic material for viewing of its contents. The plunger 12 is
of a generally cruciform shape in cross section, with inner 22 and
outer 23 end plates.
The piston 14 may be constructed of rubber or other resilient material.
At the extreme inner end of the plunger 12 there is attached a tapered
threadlock 18 as shown in FIG. 1 with the threadlock 18 having the
capability of threadedly engaging a threadbore 42 as described hereinafter.
The threadlock 18 is in the general form of the threaded portion
of a screw and the piston 14 has an axial threadport 19 through
which the threadlock 18 passes with a fluid tight fit, so that the
forward end of the threadlock 18 extends beyond the piston 14 as
shown in FIG. 2.
The cylinder 16 is provided at its outer end with a plurality of
stops or ribs 20 which engage the inner end plate 22 of the plunger
12 upon rearward movement thereof to prevent complete withdrawal
of the plunger 12 from the cylinder 16. As shown in FIGS. 1 and
4 through 7 the cruciform shaft of the plunger 12 is of reduced
diameter at the rear end so as to clear the stops 20 during rotation.
At the forward end of the cylinder 16 there is provided a neck portion
24 of reduced diameter which receives the threadbore element 26
with tapered hub portion 28 during the pre-injection stage, as shown
in FIG. 2 and with a gasket member 30 being positioned between
the threadbore 26 and the neck portion 24 to provide a fluid tight
A cannula or hollow needle 32 is received in a tapered mounting
post 34 having an axial passage 36 as shown in FIG. 4 and having
an enlarged base portion 38 which fits in fluid tight engagement
over the outer end of the hub 28. A tapered hollow sheath 40 may
be removably fitted over the needle 32 and post 34.
The threadbore 26 is provided with an inner chamber or bore 42
extending the length of the threadbore 26 and hub portion 28. The
bore 42 has threaded walls 44 adjacent the outer end of the hub
28 for engagement with the tapered threadlock 18. The hub 28 is
tapered inwardly toward the forward end thereof and the inner bore
42 is of reduced diameter within the hub portion 28.
The gasket member 30 should fit securely around the circumference
of the threadbore 26 so as to maintain its position on the threadbore
26 during axial movement and interaction with the neck portion 24
of the cylinder 16. The gasket 30 may be constructed of a resilient
material such as moderately soft polyethylene or other similar material.
In one embodiment, the gasket 30 had an outer diameter of 6 mm.
and an inner diameter of 4 mm. Once stretched over the threadbore
assembly, the combined outer diameter of the two components was
7 mm. The inner diameter of the cylinder neck 24 in this embodiment
was also 7 mm. The outer surface of the gasket 30 is temporarily
sealed to the inner surface of the cylinder neck 24 by capillary
action during operation of the device.
As the threadlock 18 engages the threadbore 26 as shown in FIG.
3 the gasket 30 should have a sufficiently tight fit within the
cylinder neck 24 to allow the threadlock 18 to press against and
engage the threadbore 26 under normal manual pressure without having
the gasket 30 pass forward through the neck 24. The forward edge
23 of the neck 24 may be rolled inwardly to produce a very slightly
smaller diameter at the margin only, as shown in FIGS. 2 through
4 so as to prevent forward movement of the gasket 30. The fit of
the gasket 30 within the neck 24 should then allow the threadbore
26 with attached gasket 30 to be withdrawn within the interior of
the cylinder 16 as shown in FIG. 4. In this regard, the diameter
of the post member 34 should be sufficiently small so as to pass
rearwardly through the cylinder neck 24 to the position of FIG.
In the use of the syringe device 10 of the present invention, the
plunger 12 and cylinder 16 may be employed in the usual manner by
moving the plunger 12 forward to expel an injectable fluid from
the cylindrical chamber, as shown in FIGS. 2 and 5. Once the fluid
has been expelled, the plunger 12 may be rotated by hand in a clockwise
direction as shown in FIGS. 3 and 6 to cause the threadlock 18 to
engage the threads 44 of threadbore 42. Generally about one half
turn of the plunger 12 should be sufficient to cause the units to
engage. After engagement of the threadlock 18 and threadbore 42
the outwardly extending portion, including hub member 28 gasket
30 post 34 and needle 32 may be withdrawn into the interior of
the cylinder 16 by pulling the plunger 12 rearwardly as shown in
FIGS. 4 and 7. In this latter position, the needle 32 is then safely
stowed for disposal.
The invention may be embodied in other specific forms without departing
from the spirit or essential characteristics thereof. The present
embodiments are therefore to be considered in all respects as illustrative
and not restrictive, the scope of the invention being indicated
by the appended claims rather than by the foregoing description,
and all changes which come within the meaning and range of equivalency
of the claims are therefore intended to be embraced therein.