Safety syringe abstract
A safety syringe having a sliding base with a hole in a barrel
to hold a locking tip to fix a needle cannula, in which the hole
has a flange at the bottom to prevent downward sliding of the locking
tip, the barrel being provided with a plurality of ventilation holes
at the front end and a limiting flange at its inner wall to prevent
from downward sliding of the sliding base so that the locking tip
is positioned for injection, and a spring disposed at the locking
tip between an end of the barrel and a needle extender so that when
a hollow plunger with a cork at the top is pushed axially to the
foremost position, the sliding base is forced to displace forwardly,
and consequently the locking tip is forced to keep close contact
with the extender and displace in an opposite direction. A further
pushing of the plunger causes the fixed locking tip to pass through
the flange at the bottom of the hole at the sliding base and then
push the cork away from the plunger by upward displacement of the
plunger. The cork, with the needle cannula and the locking tip,
are displaced into the interior space of the plunger at the end
of injection to prevent injury and infection from the used needle
cannula.
Safety syringe claims
What is claimed is:
1. A safety syringe comprising:
a) a hollow barrel having an open back end and a front end, the
front end being provided with a needle extender and a plurality
of ventilation holes;
b) a locking tip disposed within the barrel and positioned adjacent
the needle extender, and a needle cannula secured to the locking
tip and extending outwardly through the needle extender;
c) a plunger having a front end, the plunger being slidably received
in the barrel through the open back end and positioned in close
contact with an inner wall of the barrel, the plunger including
an opening at the front end communicating with an interior space
therein, and a sealing element temporarily sealing the opening;
d) a sliding base having a hole therethrough, the locking tip being
disposed within the hole, and a flange positioned at a bottom portion
of the hole for securing the locking tip therein;
e) a limiting flange on the inner wall of the barrel and disposed
in engagement with the sliding base to prevent the sliding base
from moving away from the front end of the barrel; and
f) wherein when the plunger is axially slid towards the front end
of the barrel, the front end of the plunger and sealing element
engage the sliding base and locking tip to displace the sliding
base and locking tip in opposite directions and also displace the
sealing element, so that continued movement of the plunger towards
the front end of the barrel causes the needle cannula, locking tip
and sealing element to be disposed within the interior space of
the plunger.
2. The safety syringe of claim 1 further including an elastic element
positioned within the needle extender for urging the locking tip
away from the front end of the barrel.
3. The safety syringe of claim 1 wherein the locking tip further
includes an adapter extending outwardly of the needle extender for
securing needle cannulae having different needle hubs.
Safety syringe description
BACKGROUND OF THE INVENTION
The present invention relates to a safety syringe, particularly
a simple syringe structure which can have its needle cannula retracted
into its hollow plunger after injection to assure the safety of
medical personnel and prevent reuse of the used syringe.
A conventional disposable syringe is made of plastic material and
without indicating means to show whether it is brand new or used.
A used syringe may be reused due to negligence or for lowering of
operating costs, and consequently the patient who receives an injection
with a used syringe may be infected by AIDS, hepatitis or other
diseases transmitted through body fluid contact. Moreover, medical
personnel who disposes of used syringes may be injured by a used
needle cannula or infected with diseases from contact with the used
needle cannula.
SUMMARY OF THE INVENTION
The main objective of the present invention is to provide an absolutely
safe syringe with close contact between a sliding base and a plunger
in a barrel to prevent medicine residues in the barrel after injection.
Another objective of the present invention is to provide a safety
syringe with a simple structure to permit mass production of the
syringe at the lowest possible cost.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of a safety syringe according to the
present invention.
FIG. 2 is a sectional view of the safety syringe according to the
present invention showing the syringe just before completion of
an injection process.
FIG. 3 is a sectional view of the safety syringe according to the
present invention showing the locking tip being pushed by the plunger
just before completion of an injection process.
FIG. 4 is a sectional view of the safety syringe according to the
present invention showing the disposition of the needle cannula
within the interior space of the plunger.
FIG. 5 illustrates the operation of the safety syringe without
the spring according to the present invention.
FIG. 6 is a sectional view of another embodiment of a safety syringe
according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIGS. 1 and 2 a safety syringe (10), according to
a first embodiment of the present invention, comprises a barrel
(12) having a needle extender (19) at the front end. Two ventilation
holes (41 and 42) are located besides the needle extender (19) at
the end of the barrel (12). A needle cannula (30) is fixed to a
locking tip (34) which is secured to a sliding base (20) having
a round hole (22). The hole (22) has a flange (24) at the bottom
to prevent the locking tip (34) from downward displacement. A limiting
flange (26) is provided at an appropriate location on the inner
wall of the front end of the barrel (12) to prevent the sliding
base (20) from downward displacement so that the locking tip (34)
and the sliding base (20) are positioned at a ready position. The
sliding base (20) has a ring groove (28) at a lateral side to engage
with the limiting flange (26) at the inner wall of the barrel (12)
to prevent its downward displacement. A spring (38) extends through
the locking tip (34) so that it is located between the barrel (12)
and the needle extender (19) for a needle cannula (30) which has
a passage (31) for medicine and a tip (32) for hypodermic injection
through the passage (31).
Referring to FIGS. 3 and 4 the safety syringe (10) further includes
a hollow plunger (50) made by high frequency molding or other appropriate
method for axial displacement in the barrel. The plunger (50) is
forcibly inserted into the barrel (12) from an open end (14) of
the barrel (10), with the open end (14) of the barrel (10) being
tightly sealed by a stopper (58). By the axial displacement of the
plunger (50), medicine is drawn in to fill the barrel (12) by vacuum
pressure, or expelled from the barrel (12) through the passage (31)
at the needle cannula (30). The plunger (50) has a cork element
(56) at its front end and seal the open end (14) of the barrel (12)
to form a tightly closed space within the barrel (12). The cork
element (56) is designed so that it can enter into the tightly closed
space by operation of a thumb rest (57) provided at the other end
of the plunger (50). Before each injection, the plunger (50) is
pulled backwards to generate a vacuum pressure in the barrel (12)
in order to draw medicine into the barrel (12) through the passage
(31) at the needle cannula (30).
For injection, the tip (32) of the needle cannula (30) is first
placed into a patient'skin and then the plunger (50) is pushed forward
to inject the medicine from the barrel (12) through passage (31)
into the patient's body. As soon as the plunger reaches its foremost
position, the stopper (58) expels all the medicine out of the barrel
(12), and maintains close contact with the bottom of the sliding
base (20). When the plunger (50) is pushed further, the locking
tip (34) is caused to push against the extender (19). Consequently,
the extender (19) and the sliding base (20) are displaced in opposite
directions. A further pushing of the plunger (50) causes the fixed
locking tip (34) to pass through the flange (24) at the bottom of
the hole (22) at the sliding base (20) by upward displacement of
the plunger (50) during which the top of the plunger (50) continues
to push the sliding base (20). By the upward pushing force from
the plunger (50), the locking tip (34) reacts and push the cork
(56) out of the open end (54) of the plunger (50). Then, the needle
cannula (30) is only supported by the patient's muscle where the
needle cannula (30) is pierced, the needle cannula (30) and the
locking tip (34) are temporarily maintained at this injection position.
After completion of the injection, as soon as the needle cannula
(30) is pulled out of the patient's body, the needle cannula (30)
and the locking tip (34) do not have any support, and hence they
are brought into the internal space of the plunger (50) though the
open end (54) formed by the displaced cork (56). The barrel (12)
is designed with a plurality of ventilation holes (41 and 42) at
the front end to facilitate injection.
The barrel (12) has a limiting flange (11) and the plunger (50)
has a corresponding limiting flange (59). These limiting flanges
(11 and 59) are designed to prevent the plunger (50) from backward
displacement when it reaches the foremost position and to minimize
space required for maintaining used syringe (10).
Referring to FIG. 5 there is shown another embodiment of the present
invention which does not have an element. It is mainly characterized
by fixing of the locking tip (34) to the extender (19) at the top
of the barrel (12) through the hole (22) at the sliding base (20)
so that the syringe is ready for injection. As soon as the plunger
(50) is pushed axially and reaches its foremost position, the sliding
base (20) is pushed forwardly so that the fixed locking tip (34)
and the sliding base (20) subjected to pushing by the plunger (50),
are displaced in opposite directions. When the plunger (50) is pushed
further, the sliding base (20) is compressed by the plunger (50)
so that the bottom of the locking tip (34) is forced to pass through
the flange (24) at the hole (22) of the sliding base (20), and engage
the cork (56) at the foremost end of plunger (50). Consequently,
the locking tip (34) and the cork (56) are displaced and fall into
the interior space of the plunger (50).
Referring to FIG. 6 there is shown another embodiment according
to the present invention. The needle cannula (30) and the needle
hub (27) used here are of conventional structure, and different
types of needle cannula are available in the market for injection
to different parts of the human body. The locking tip (34) is incorporated
with an adapter (60) for fixing of the needle cannula (30) and the
needle hub (27). The adapter (60) is designed with a passage (61)
to connect the barrel (12) to the passage (31) of the needle cannula
(30) for suction and injection of medicine. The retraction of the
locking tip (34) with the adapter (60) carrying the needle hub (27)
and the needle cannula (3) into the interior space of the plunger
(50) are identical to that previously described and shown in FIGS.
1 through 5.
As clearly shown by the injection process illustrated by the drawings,
the safety syringe according to the present invention has a simple
structure with a plunger (50) for pushing a sliding base (20) into
closing contact with a barrel's inner wall to the foremost position
to minimize residual medicine in the barrel (12), and a needle cannula
(30) having a locking tip (34) which are displayed into the interior
space (42) of the plunger (50) by action of a spring (38) because
there is no support for the needle cannula (30) and the locking
tip after injection so that the needle cannula (30) will not be
exposed to the environment. With such a structure, injury and infection
by a used needle cannula can be prevented.
As indicated, the structure herein may be variously embodied. Recognizing
various modifications will be apparent, the scope thereof shall
be deemed to be defined by the claims as set forth below. |