Note: Descriptions are shown in the official language in which they were submitted.
CA 02547237 2006-05-18
SYRINGE BARREL AND SYRINGE USES THE SAME
Field of the Invention:
The present invention relates to syringe barrels, more particularly to a
syringe barrel and syringe uses the same wherein a needle mount and a
needle hub of the syringe will be coupled with precision.
Background of the Invention:
A safety syringe of the prior art is characterized by a syringe barrel
capable of pulling a needle back therein after an injection, so as to prevent
reusing it. At the same time, the syringe is safer to abandon with the needle
hidden.
Accordingly, the safety syringe of the prior art comprises a syringe
barrel, a push rod, a needle hub and a syringe needle. The needle hub is
mounted on the front face of the barrel for housing a needle mount. The
connection of the needle mount into the needle hub should be at one hand
tight, at the other hand retractable, so that the needle can be pulled back
into the barrel by the push rod. To achieve the objective, the rear end of the
needle mount where the needle hub is engaged is provided with a receptacle
hole of large radius. The receptacle hole is further provided with a neck
section, and the front terminal of the push rod has a hooked conic head.
Thereby, as the push rod inject a solution out of the barrel, the hooked conic
head will be embedded into the receptacle hole and hooked with the needle
mount. As the push rod id pulled backward, the needle will also be pulled
into the barrel.
However, the needle mount of the prior art should be made with
precision so as to assure the pulling back of the needle, which is a difficult
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manufacturing task and therefore expensive. Further, to assure the pulling
back of the needle, the drag between the needle mount and the barrel must
be lessened, therefore sacrificing the tightness of the connection. As a
result, the needle structure is likely to let go if the drag of a human body
is
too large, invalidating an injection. It is a further disadvantage that the
solution in the barrel may leak through where the needle mount and the
needle hub of the barrel, leading to a drop of the needle.
On the other hand, if the connection between of needle mount and the
needle hub is too tight, the conic head of the push rod will depart from the
receptacle hole as it is being pulled back. Therefore, the purpose of safety
use cannot be attained.
To summarize, the conventional needle mount made of hard plastic
materials needs a high-precision injection molding to solve the above
dilemma, which is expensive to the manufacturer and therefore the cost of
the safety syringes is high. Further, the needle hub attached to the syringe
barrel could be slightly deformed due to high temperature in the storage
space, which is another factor influences the required precision.
Summary of the Invention:
Accordingly, the syringe barrel and syringe uses the same wherein the
syringe barrel comprises a round plastic bracket at the front end of the
barrel, which defines a. needle hub; the bracket is formed at the same time
when the barrel is molded. The bracket is further covered by a rubber
flexible member through injection molding. The radius of the inner rim of
the flexible member is smaller than that of the outer radius of a needle
mount, whereby the needle mount will be coupled tightly with a needle hub
using the bracket of the barrel. The elastic deformation of the inner space of
the flexible member will provide the effect of pinching the needle mount,
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which achieves a precision coupling with a low cost.
The various objects and advantages of the present invention will be
more readily understood from the following detailed description when read
in conjunction with the appended drawings.
Brief Description of the Drawings:
Fig.l is side cross sectional view of a syringe of the present invention.
Fig.2 is local cross sectional view of the syringe in Fig.l.
Fig.3 is local perspective view of the syringe in Fig.l.
Fig.4 is local perspective view of the second preferred embodiment of
the present invention.
Fig.S is another local perspective view of a syringe and a needle hub of
the present invention.
Fig.6 is a cross sectional view of the syringe and the needle hub in
Fig.S.
Fig.7 is local perspective view of the second preferred embodiment of
the present invention, showing the barrel and the needle hub.
Fig.8 is a cross sectional view of the syringe and the needle hub in
Fig.7.
Detailed Description of the Preferred Embodiments:
Referring to Figs.l and 2, a syringe barrel according to the present
invention comprises a barrel 10 being a hollow cylinder and a needle hub 11
of radius smaller than that of the barrel 10 extended from the front end of
the barrel 10. The rear end of the barrel 10 is provided with a finger flange
12 which is an enlarged and extended portion thereof. The inner space of
the barrel 10 defines a plunger receptacle 13 which is extended out of the
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barrel 10 from the rear end.
The syringe 'further includes a thumb rest 14 coupled within the plunger
receptacle 13 of the barrel 10. At the front end of the thumb rest 14, there
forms a stopper 141 taking the shape of a block of round cross section; at
the rear end of the thumb rest 14, there forms a thumb support 142 bigger
than the cross section of the plunger receptacle 13.
The syringe further includes a needle structure 15 comprising a round
needle mount 151 being an elongated section and a needle cannula 152
being a long, hollow needle. The round needle mount 151 and the needle
hub 11 form a stable connection as the round needle mount 151 is engaged
with the annularly distributed bulges 1 on the inner wall of the needle hub
11. Further, one end of the needle mount 151 is provided with a recessed
retaining groove 153.
Referring to Figs.3, 5 and 6, a needle hub 11 of radius smaller than that
of the barrel 10 is extended from the front end of the barrel 10. As the
barrel
10 was first formed, the front end thereof is extended to form a plastic
bracket 16, which is a bundle of parallel bulged columns 161. The free end
of the collection of bulged columns 161 is provided with a round ring 162
connecting the columns 161, whereby the structure of the needle hub 11 is
strengthened.
The outer layer of the bracket 16, which indicates the inner and outer
rims thereon, is provided with a flexible member 17 made of plastic rubber.
The connection of the flexible member 17 to the bracket 16 is done by
injection coating or injecting a plastic sleeve corresponding to the inner and
inner rims of the bracket 16 on the bracket 16. No matter which connection
way, the plastic material of the flexible member 17 possess a property of
varying the space therein, whereby the connection between the needle
mount 151 and the needle hub 11 can be tight, achieving not only a
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high-precision connection but also a retractable coupling by a push rod. The
latter function makes the syringe not reusable.
Further, the above-mentioned flexible member 17 has an inner radius
less than that of the outer radius of the round needle mount 151. Since the
S inner a inner rim of the flexible member 17 forms an inner flange 171, the
needle mount 151 will be retained by the flexible member 17 as the needle
mount 151 inserted into the needle hub 11.
The present invention and the conventional needle hub and needle
mount differ in that the latter is made of a hard plastic material. However,
since that the bracket 16 is made of a hard plastic material and the flexible
member 17 is made of flexible rubber, the inner space of the flexible
member 17 is flexsible. Further, the inner radius of the flexible member 17
is slightly smaller than that of a needle mount 151, whereby the needle
mount 151 will be erected with precision due to the flexibility of the
flexible member 17.
This design has the following advantages. First, since the rubber
material making the flexible member 17 is superior in changing the shape of
its receptacle space, the tight connection between the needle mount and the
needle hub will thus be assured. Thereby, the needle mount cannot be easily
pulled out.
Second, to pull out the needle mount from the needle hub, a proper
force exerted on the needle mount will suffice; an extremely large force is
not necessary.
Third, the flex member around the inner rim of the needle hub can be
implanted by regular injection molding, achieving a tight connection of the
needle mount to the needle hub.
To be consistent, the bracket 16 is made of a plastic material, the same
as that of the needle hub. Since the bracket 16 is formed at the same time
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the barrel 10 is being made, the connecting structure of needle hub is tough.
Further, the bracket 16 i.s provided with a bundle of columns 161, forming a
rib structure by which the friction between the mount and the hub is
enhanced, achieving tight connection between the two.
The above structure is valid for syringes of 3-5 ce. Syringes less than 1
cc is not applicable, because the contact area between the needle mount and
the needle hub is getting smaller. As the thumb support and the associated
push rod are being pushed forward, most of the pressure will be
concentrated on the bottom face of the mount, inevitably leading to a
departure of the mount from the hub, since the pressure force exceeds the
frictional drag.
On the other hand, the present invention can be used to syringes less
than 1 cc, as shown in Figs.4, 7 and 8. Although the contact area between
the needle mount 151 a.nd the needle hub 11 is getting smaller, the flexible
member 17 of the hub 11 provides extra pinch to the needle mount 151 and
therefore enhances the connection. The connection is further strengthened
by the annular inner flange 171 within the flexible member 17 and, further,
the retaining groove 153 therein.
The present invention is thus described, and it will be obvious that the
same may be varied in many ways. Such variations are not to be regarded as
a departure from the spirit and scope of the present invention, and all such
modifications as would be obvious to one skilled in the art are intended to
be included within the scope of the following claims.
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