Safety syringe abstract
A safety syringe ensuring stable and airtight connection of a hub
to a barrel of the syringe is provided. A rear portion of the hub
is tightly fitted in a neck portion at a front end of the barrel,
such that the hub is prevented from moving out of the barrel via
the neck portion. A first airtight contact line is formed at joint
of two shoulder portions separately formed on the hub and the neck
portion, and a second airtight contact line is formed at a position
within a contact surface between the hub and the neck portion, so
that the hub is stably and air-tightly connected to the barrel.
A plunger is disposed in the barrel to push medical liquid in the
barrel into the hub and a cannula fixed to the hub for injection
purpose. An engaging cone having a slit is forward projected from
a front end of the plunger to engage into receiving holes formed
on the hub when the plunger is fully push forward. Any residual
medical liquid in the barrel between the plunger and the hub flows
backward via the slit to eliminate internal pressure in the barrel
and thereby enables smooth injection of medical liquid into a patient's
body.
Safety syringe claims
What is claimed is:
1. A safety syringe, comprising a barrel, a hub, a cap and a plunger;
said barrel including a diameter-reduced neck portion extending
to an open front end portion, said open front end portion having
a radially inwardly inclining inner peripheral wall forming a first
shoulder portion between said inner peripheral wall of said open
front end portion and an inner peripheral wall of said neck portion,
said inner peripheral wall of said neck portion being gradually
diametrically reduced from said first shoulder portion to a rear
end of said neck portion;
said hub having (a) a cannula fixed to a front end thereof, (b)
a second shoulder portion circumscribing a middle portion of said
hub, and (c) a radially extending channel formed adjacent a rear
end of said hub and defining a pair of diametrically opposed openings
therein to serve as receiving holes, an outer peripheral wall portion
having a gradually reduced diameter between said second shoulder
portion and said rear end of said hub;
said cap removably covering said cannula and a portion of said
hub; and,
said plunger being removably disposed in said barrel for injecting
a medical liquid from within said barrel into a patient's body through
said cannula, said plunger being an elongated member inserted into
said barrel via an opening provided at a rear end of said barrel,
said plunger having a stopper provided around a front end thereof
with an engaging cone projecting forward from a front end of said
stopper, said engaging cone being formed with a small slit extending
radially from a pointed end of said engaging cone to a peripheral
edge thereof, whereby when said hub is assembled into said neck
portion of said barrel, said first and second shoulder portions
are disposed in contact with each other to (a) provide a first airtight
contacting surface joint therebetween, and (b) prevent said hub
from moving out of said neck portion of said barrel, and said outer
peripheral wall portion of said hub engaging said inner peripheral
wall of said neck portion in substantially conformed manner to form
a second airtight contacting surface joint therebetween.
2. A safety syringe comprising:
a barrel including a diameter-reduced neck portion extending axially
therefrom, said neck portion having terminating at an open front
end portion, said open front end portion defining an inclined first
inner peripheral wall extending axially rearward and radially inward
to form a first shoulder portion, said neck portion defining a second
inner peripheral wall extending from said first shoulder portion
in gradually diametrically reduced manner to a rear end thereof;
a hub coaxially coupled to said barrel having a cannula fixed to
a front end thereof, said hub having an intermediate portion extending
axially from said front end to a rear end, said hub including a
second shoulder portion circumscribing said intermediate portion
for engaging said first shoulder portion of said barrel, said intermediate
portion having formed therein adjacent said rear end a pair of diametrically
opposed receiving hole openings, said intermediate portion defining
an outer peripheral wall portion frictionally engaging said second
inner peripheral wall of said barrel neck portion in substantially
flush manner, said outer peripheral wall portion being gradually
reduced in diameter between said second shoulder portion and said
rear end;
a cap removably covering said cannula and at least a portion of
said hub; and,
a plunger removably disposed in said barrel for injecting a medical
liquid from within said barrel into a patient's body through said
cannula, said plunger being an elongated member inserted into said
barrel via an opening provided at a rear end of said barrel, said
plunger having a stopper disposed at a front end thereof and an
engaging cone projecting axially from a front end of said stopper
for engaging said receiving hole openings of said hub intermediate
portion upon substantially full insert of said plunger into said
barrel;
said first and second shoulder portions forming a first airtight
contacting surface joint therebetween when said hub is assembled
with said neck portion of said to prevent detachment of said hub
from said barrel neck portion, and said outer peripheral wall portion
of said hub forming a second airtight contacting surface joint against
said inner peripheral wall of said barrel neck portion.
3. The safety syringe as recited in claim 2 wherein said engaging
cone has formed to extend axially therethrough at least one exhaust
opening, whereby pressure accumulation adjacent said engaging cone
is prevented.
Safety syringe description
BACKGROUND OF THE INVENTION
In the medical practices of early days, a used syringe would be
thoroughly sterilized for repeated use later. Any incomplete serialization
would dangerously cause a second time infection of a patient and/or
any other people. To avoid such second time infection, disposable
syringes are largely produced. However, large amount of discarded
disposable syringes also bring us new problems of environmental
pollution and safety of syringes in use. This is because no specific
measures have been taken in disposing cannulas of the discarded
syringes and exposed cannulas tend to easily stab nursing or cleaning
personnel and result in even more infected people. To prevent discarded
syringes and/or cannulas from unexpectedly stabbing and therefore
undesirably injuring and infecting other people, including nursing
and cleaning persons, various types of safety syringes are particularly
developed, such as those disclosed in U.S. Pat. Nos. 5562627;
5405327; 5569203; 5899887; 5395346 etc. All of these previously
disclosed syringes have specially associated hubs and barrels, so
that hubs and cannulas held thereto of used syringes can be pulled
back into the barrels without the risk of unexpectedly stabbing
other people.
However, all these safety syringes of prior art having retractable
hub and cannula developed to improve conventional syringes have
a common issue, that is, the hubs of these safety syringes must
be able to be stably connected to the barrels and be pulled back
into the latter after the syringes have been used, while the hubs
must be connected to the barrels in an absolutely airtight manner
that is very important factor in providing good quality safety syringes.
As it is known that, when the hub is tightly connected to the barrel
to ensure a good airtightness at the joint of these two members,
it would be difficult to pull the hub back into the barrel easily;
and when the easiness of pulling the hub back into the barrel is
considered, it would be inevitable to sacrifice the airtightness
between the hub and the barrel.
In the conventional retractable safety syringe, the hub and the
used cannula are pulled back into the barrel by engaging a forward
projected conic member on the plunger with holes provided on the
hub. However, experiences in using such conventional retractable
safety syringe indicate that an airtight small space is formed between
the hub and the plunger when the latter is about to be fully pushed
into the barrel to contact with the hub. At this point, any residual
medical liquid in the hub would form a resistance to the tight engagement
of the hub with the engaging conic member on the plunger. A nursing
personnel needs to apply an increased force to push the plunger
forward to ensure the full engagement of the conic member with the
hub. Such increased force would cause a vibrating syringe and discomfort
the patient.
It is therefore tried by the inventor to develop an improved safety
syringe to eliminate the drawbacks existing in the conventional
retractable safety syringe.
SUMMARY OF THE INVENTION
A primary object of the present invention is to provide an improved
safety syringe, a barrel of which has a first shoulder provided
in a neck portion thereof and a hub of which has a second shoulder
provided around a middle portion thereof, such that the hub is retained
to the neck portion by engagement of the first and the second shoulders
with each other when the hub is pushed backward into the neck portion,
and that an airtight contact line is formed at joint of the two
shoulders to ensure airtight connection of the hub to the barrel.
Another object of the present invention is to provide an improved
safety syringe, of which the neck portion of the barrel has an inner
peripheral wall gradually diametrically reduced backward and the
hub has an outer peripheral wall gradually diametrically reduced
backward, and the hub has an outer diameter slightly larger than
an inner diameter of the neck portion of the barrel, such that the
hub is stably received in the neck portion in the manner of tight
fit.
A further object of the present invention is to provide an improved
safety syringe, of which the hub and the neck portion of the barrel
is so designed in their diameters, lengths and inclinations that
a second airtight contact line is formed at a certain position within
the contact surface between the hub and the neck portion.
A still further object of the present invention is to provide an
improved safety syringe, a plunger of which is provided at a front
end with an engaging cone having a small slit. The engaging cone
is adapted to engage into two receiving holes formed on the hub
of the syringe when the syringe has been fully pushed forward in
the barrel. The slit on the engaging cone allows residual medical
liquid in the barrel between the plunger and the hub to flow backward
into the barrel to enable smooth push of the plunger fully into
the barrel.
BRIEF DESCRIPTION OF THE DRAWINGS
The structure and the technical means adopted by the present invention
to achieve the above and other objects can be best understood by
referring to the following detailed description of the preferred
embodiments and the accompanying drawings, wherein
FIG. 1 is an exploded perspective of a conventional safety syringe;
FIG. 2 is a partially exploded perspective of a safety syringe
according to the present invention;
FIG. 3 is a fragmentary sectional view showing a hub of the safety
syringe of FIG. 2 before being engaged into a barrel of the safety
syringe of FIG. 2;
FIG. 4 is a fragmentary sectional view showing that the hub of
FIG. 3 has been engaged into the barrel of the safety syringe of
FIG. 2;
FIG. 5 is a fragmentary sectional view showing that a cap covering
the hub is removed to expose a cannula mounted on the hub after
the hub has been engaged into the barrel;
FIG. 6 is a fragmentary sectional view showing that a plunger of
the safety syringe of FIG. 2 is fully pushed forward to engage a
front end thereof with the hub; and
FIG. 7 is a fragmentary sectional view showing the hub and the
cannula are pulled backward by the plunger into the barrel when
the cannula has been used.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Please refer to FIG. 2 that is a partially exploded perspective
of a safety syringe according to the present invention. The safety
syringe of the present invention mainly includes a barrel 1 a plunger
2 a hub 3 and a cap 4.
The barrel 1 has a diameter-reduced neck portion that defines a
front open end of the barrel 1. An inner peripheral wall 11 of the
front open end of the neck portion inclines radially inward, so
that a first shoulder portion 13 is formed between the inclined
peripheral wall 11 and an inner peripheral wall 12 of the neck portion
behind the inclined peripheral wall 11. The inner peripheral wall
12 of the neck portion is gradually diametrically reduced from an
end having the first shoulder portion 13 toward a rear end of the
neck portion.
The plunger 2 is extended into the barrel 1 via an opening provided
at a rear end of the barrel 1. A stopper 21 is provided around a
front end of the plunger 2 with an engaging cone 22 forward projected
from a front end of the stopper 21. And, there is a small slit 23
radially extended from a point of the engaging cone 22 to a peripheral
edge thereof.
The hub 3 has a cannula 31 fixed to a front end thereof, and is
formed near and around a middle portion thereof with a second shoulder
portion 32 and at a rear portion thereof with a radially extended
channel which defines two diametrically opposite openings on the
hub to serve as two receiving holes 33. An outer peripheral wall
of a rear portion of the hub 3 behind the second shoulder portion
32 is gradually diametrically reduced toward a rear end of the hub
3.
The cap 4 is removably covered over the hub 3 and the cannula 31.
In assembling the safety syringe of the present invention, first
extend the hub 3 and the cannula 31 fixed thereto into the cap 4.
The cap 4 is so designed that it has an inner diameter similar to
an outer diameter of a portion of the hub 3 above the second shoulder
portion 32 so that the cap 4 is assembled to the front end of the
hub 3 in the manner of tight fit, as shown in FIG. 3. Then, position
the hub 3 into the barrel 1 by pushing the hub 3 rearward against
the front open end of the neck portion until the second shoulder
portion 32 of the hub 3 passes the radially inward inclined inner
peripheral wall 11 and the first shoulder portion 13 as shown in
FIG. 4. At this point, a first airtight contact line 34 is formed
around a joint of the first and the second shoulder portions 13
and 32 and the hub 3 is tightly fixed in the neck portion of the
barrel 1 and could no longer be moved out from the front open end
of the neck portion. The gradually diametrically reduced outer peripheral
wall of the rear portion of the hub 3 and the gradually diametrically
reduced inner peripheral wall 12 of the neck portion of the barrel
1 are so designed in their diameters, lengths and inclinations that
a second airtight contact line 35 is naturally formed around a certain
position on a contact surface between the hub 3 and the neck portion
when the hub 3 is tightly received in the neck portion. These two
airtight contact lines 34 and 35 together ensure perfectly stable
and airtight connection of the hub 3 to the barrel 1.
Finally, pull the cap 4 forward to expose the cannula 31 as shown
in FIG. 5 and the safety syringe of the present invention is ready
for injection. When the plunger 2 is pushed forward in the barrel
1 for the purpose of injection medical liquid and the engaging cone
22 at the front end of the stopper 21 on the plunger 2 is about
to engage into the receiving holes 33 on the hub 3 any residual
medical liquid in the barrel 1 is compressed by further movement
of the plunger 2 toward the hub 3 and is brought to partially flow
backward into the slit 23 radially provided on the bevel head of
the engaging cone 22 allowing the plunger 2 to be further and smoothly
pushed forward into the hub 3 without being stopped by an internal
pressure between the stopper 21 of the plunger 2 and the hub 3
as shown in FIG. 6. With the slit 23 the problem of an overly strong
push of the plunger 2 that would cause discomfort of patient being
injected and an undesirable jetted medical liquid from the cannula
31 could therefore be avoided. After the injection, the plunger
2 is pulled backward to bring the hub 3 engaged with the engaging
cone 22 of the plunger 2 and the used cannula 31 fixed to the hub
3 to move backward out of the neck portion and into the barrel 1
as shown in FIG. 7.
With the above arrangements, the safety syringe of the present
invention in a fully assembled state is provided with two airtight
contact lines 34 and 35 between the hub 3 and the barrel 1 to ensure
firm, stable and airtight connection of the hub 3 and the cannula
31 to the barrel 1 and to eliminate drawbacks existing in the conventional
retractable safety syringes. The safety syringe of the present invention
is therefore novel, improved and practical for use. |