Safety syringe abstract
A safety syringe has a retaining device formed on a front end of
the barrel, multiple bosses formed on the needle hub to rotatably
correspond to the retaining device, multiple recesses defined inside
the needle hub and multiple inclined teeth formed on the plunger
to correspond to the recesses, such that the engagement between
the retaining device and the bosses of the needle hub is able to
be released by the rotational movement of the plunger together with
the needle hub due to the combination of the inclined teeth and
the recesses.
Safety syringe claims
What is claimed is:
1. A safety syringe comprising: a barrel having a through hole
axially defined therein and a retaining device formed inside a front
end of the barrel; a plunger slidably received in the barrel and
having a neck formed on a front end thereof so as to allow a rubber
seal to fit in, a conical head projecting from the neck, multiple
spatially formed inclined teeth, and a flange oppositely formed
on the plunger to conical head; a needle hub detachably engaged
with the barrel and having a conical front end with multiple bosses
formed to rotatably correspond to the retaining device of the barrel,
an axially defined hole corresponding to and being in communication
with the through hole of the barrel, a receiving hole defined to
communicate with the hole and the through hole of the barrel and
to allow the extension of the conical head of the plunger, multiple
recesses defined to receive the inclined teeth and a shoulder defined
in a periphery of the receiving hole to correspond to the conical
head of the plunger; and a needle having a sleeve securely engaged
with the conical front head of the needle hub and a metal tube securely
engaged with the sleeve; wherein the bosses are rotatably released
from the clamp of the fingers by the engagement of the inclined
teeth and the recesses.
2. The syringe as claimed in claim 1 wherein the retaining device
comprises multiple L shaped fingers formed to clamp the bosses and
multiple troughs defined to receive the bosses.
3. The syringe as claimed in claim 2 wherein a resilient push
rod is formed on an end of the conical head to be received in and
abutted to an inner periphery of the receiving hole of the needle
hub.
Safety syringe description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a syringe, and more particularly
to a safety syringe, which has a ratchet device formed on the needle
hub and an annular inclined teeth formed on one end of the plunger,
such that when the hollow barrel is pushed toward the needle hub,
the engagement between the ratchet device and the inclined teeth
is able to pull the needle hub together with the needle inside the
barrel when the barrel is pulled backward to prevent people from
being punctured by the used needle.
2. Description of Related Art
A plastic cap is always mounted on the hollow barrel of a syringe
to cover the needle to keep people from being punctured by the used
needle. However, because the user must hold the conventional cap
when he or she puts the cap onto the hollow barrel, the user is
easily punctured by the needle. In addition, the used needle must
be destroyed by melting or burning to prevent the spread of disease.
However, hazardous gas will form when the needle with the plastic
cap and needle hub is melted or burned.
In another conventional embodiment, a safety device is formed with
the syringe to prevent the user from being punctured. Clamps are
formed on the needle hub and the plunger of the syringe. When the
plunger is fully pushed into the hollow barrel of the syringe, the
clamps will engage with each other. The needle hub with the needle
will release from and be pulled fully into the barrel when the plunger
is pulled back. The used needle will be fully enclosed and held
in the hollow barrel to keep the needle from touching or puncturing
anyone.
However, a specific mold is required to form the clamps. The cost
for manufacturing the syringe with the conventional safety device
is expensive. In addition, because the entire syringe including
the hollow barrel, plunger and the hub must be melted or burned
with the needle, hazardous gas is still generated.
In order to reduce the fabrication cost, the market focuses on
the development to introduce an improved syringe to pull the used
needle inside the barrel. With reference to FIG. 1 a conventional
safety syringe comprises a hollow barrel (10), a plunger (20), a
needle hub (30) and a needle (40).
The needle hub (30) defines a receiving hole (301) in a rear end
of the needle hub (30) and a shoulder (302) is formed inside the
receiving hole (301). The plunger (20) has a conical head (201)
formed on a front end of the plunger (20) to correspond to the receiving
hole (301). With this arrangement, when the plunger (20) is moving
inside the barrel (10) toward the needle hub (30) and eventually
engages with the needle hub (30), the conical head (201) will have
an interference fit inside the receiving hole (301). Because the
formation of the shoulder (302), the conical head (201) is secured
inside the receiving hole (301) after the plunger (20) is pushed
all the way to the end of the hollow barrel (10), such that when
the plunger (20) is pulled backward inside the barrel (10), the
needle hub (30) together with the needle (40) is able to be pulled
inside the barrel (10) simultaneously, as shown in FIG. 2.
However, to facilitate the needle hub (30) to be pulled inside
the barrel (10), the engagement between the needle hub (30) and
the barrel (10) should be loose otherwise the friction between the
needle hub (30) and an inner periphery of the barrel (10) will overcome
the connection between the plunger (20) and the needle hub (30)
and the needle hub (30) can not be pulled back into the barrel (10)
successfully. In the mean time, if the engagement between the needle
hub (30) and the barrel (10) is loose, the solution inside the barrel
will have a leak and the injection can not be successful. Further,
when the needle (40) is inserted into a container (50) through the
cork (51), the needle hub (30) may retract back into the barrel
(10). However, if the engagement between the needle hub (30) and
the barrel (10) is increased, the force required to pull the needle
hub (30) together with the needle (40) back to the barrel (10) is
also increased, which causes an extra burden to the users.
With reference to FIG. 5 whether reducing the diameter of the
receiving hole (301) or increasing the diameter of the conical head
(201) to increase the engagement force between the needle hub (30)
and the barrel (10) will inevitably increase the difficulty of inserting
the conical head (201) into the receiving hole (301) and this is
the last thing that the user wants to see.
To overcome the shortcomings, the present invention intends to
provide an improved safety syringe to mitigate or obviate the aforementioned
problems.
SUMMARY OF THE INVENTION
The primary objective of the invention is to provide a syringe
enabling to release the limitation of the barrel to the needle hub
so that the needle hub with the needle is able to be pulled backward
into the barrel easily.
Another objective of the invention is to provide a syringe that
is able to provide a seal to the solution inside the barrel by the
engagement between the needle hub and the barrel, such that there
is no leak even though the needle hub is slidably engaged with the
barrel.
Still, another objective of the invention is to provide an improved
syringe with a ratchet device formed on one end of the needle hub
and inclined teeth formed on one end of the plunger to correspond
to the ratchet device of the needle hub, such that the engagement
between the ratchet device and the inclined teeth will facilitate
the retraction of the needle hub together with the needle back into
the barrel.
Other objects, advantages and novel features of the invention will
become more apparent from the following detailed description when
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross sectional view of a conventional syringe;
FIG. 2 is a cross sectional view of the syringe of FIG. 1 wherein
the needle hub is pulled back into the barrel;
FIG. 3 is a schematic view showing that the needle hub together
with the needle is pushed backward into the barrel due to the loose
connection between the needle hub and the barrel;
FIGS. 4 and 5 are cross sectional views showing that the configuration
of the conical head or the receiving hole is changed to increase
the connection between the barrel and the needle hub;
FIG. 6 is an exploded perspective view of a syringe in accordance
with the present invention;
FIG. 7 is a partially sectioned and enlarged perspective view of
the front end of the barrel in accordance with the present invention;
FIG. 8 is a partially sectioned and enlarged perspective view of
the needle hub in accordance with the present invention;
FIGS. 9 and 10 are cross sectional side views showing the movement
of the plunger inside the barrel to connect with the needle hub;
FIG. 11 is a cross sectional side plan view showing the rotation
of the plunger to securely connect with the needle hub; and
FIG. 12 is a cross sectional side plan view showing the needle
hub together with the needle is pulled backward into the barrel.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
With reference to FIG. 6 a syringe in accordance with the present
invention has a barrel (1), a plunger (2), a needle hub (3) and
a needle (4).
As shown in FIGS. 6 and 7 the barrel (1) defines axially therein
a through hole (11) and has a retaining device (110) formed on a
front end of the barrel. The retaining device has multiple equally-spaced
fingers (111) formed on an inner periphery defining the through
hole (11) and troughs (112) each defined between two adjacent fingers
(111). Each of the fingers are L shaped hence each of the troughs
(112) are also L shaped.
With reference to FIG. 6 again, the plunger (2) has a neck (21)
formed on a front end thereof so as to allow a rubber seal (22)
to fit in, a conical head (23) projecting from the neck (21), multiple
spatially formed inclined teeth (24), a resilient push rod (25)
formed on an end of the conical head (23) and a flange (26) oppositely
formed on the plunger (2) to the resilient push rod (25).
With reference to FIGS. 6 and 8 the needle hub (3) has a conical
front end (31), multiple bosses (32) formed on a periphery of the
front end (31) to correspond to the troughs (112) of the barrel
(1), an axially defined hole (33), a receiving hole (34) defined
to communicate with the hole (33), multiple recesses (35) defined
in a periphery of the receiving hole (34) to correspond to the inclined
teeth (24) and a shoulder (36) defined in the periphery of the receiving
hoe (34) and above the recesses (35) to correspond to the conical
head (23) of the plunger (2).
The needle (4) comprises a sleeve (41) and a metal tube (42).
When the syringe of the invention is assembled, the needle hub
(3) is inserted into the sleeve (41) of the needle (4) to have an
interference fit with the needle (4). Then, the needle hub (3) together
with the needle (4) is inserted into the barrel (1) to allow each
of the bosses (32) to be received in a corresponding one the troughs
(112) and clamped by the L shaped fingers (111). By doing do, a
rotation to the needle hub (3) and the needle (4) has to be implemented
so that the bosses (32) are able to be received in the troughs (112).
With such an arrangement, the needle hub (3) together with the needle
(4) is able to have a secure connection with the barrel (1). A worry
that the needle hub (3) and the needle (4) may be pushed inside
the barrel (1) while the needle is inserted into the cork (51) of
FIG. 3 is avoided. When the syringe in accordance with the present
invention is in use, the user inserts the plunger (2) into the barrel
(1). Due to the rubber seal (22) securely received in the neck (21)
of the plunger (2), the medical solution inside the barrel (1) is
able to be completely injected out of the barrel (1).
With reference to FIG. 9 after the solution is empty inside the
barrel (1), the user continuously pushes the plunger (2) to force
the conical head (23) and the. push rod (25) to extend into the
receiving hole (34) and thus allows the resilient push rod (25)
to rest inside the inner periphery of the hole (33). When the conical
head (23) of the plunger (2) extends into the receiving hole (34),
the inclined teeth (24) is received in the recesses (35) and the
joint between the neck (21) and the conical head (23) engages the
shoulder (36), as shown in FIG. 10.
Thereafter, with reference to FIG. 11 the user rotates the plunger
(2) to allow the engagement between the inclined teeth (24) and
the recesses (35) to simultaneously rotate the needle hub (3) to
release the limitation of the L shaped fingers (111) to the bosses
(32). After the limitation of the fingers (111) to the bosses (32)
is released, the engagement of the conical head (23) to the shoulder
(36) enables the user to pull the needle hub (3) together with the
needle (4) back into the barrel (1).
With reference to FIG. 12 when the needle hub (3) together with
the needle (4) is pulled back into the barrel (1), the resilient
push rod (25) will press against the needle hub (3) together with
the needle (4) to offset the alignment of the needle hub (3) together
with the needle (4) to the through hole (11) of the barrel (1),
such that a reuse to the syringe is impossible.
Even though numerous characteristics and advantages of the present
invention have been set forth in the foregoing description, together
with details of the structure and function of the invention, the
disclosure is illustrative only, and changes may be made in detail,
especially in matters of shape, size, and arrangement of parts within
the principles of the invention to the full extent indicated by
the broad general meaning of the terms in which the appended claims
are expressed.
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