Disposable safety syringe

Details Disposable safety syringe Disposable safety syringe

2001-10-26

2003-12-02

Thanh, LoAn H. (Department: 3763)

Surgery

Means for introducing or removing material from body for...

Treating material introduced into or removed from body...

C604S110000

Reexamination Certificate

active

06656165

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention is related to a disposable safety syringe. The inner circumference of front end of the barrel of the syringe is formed with a conic section. When the piston stem is forcedly pushed inward to drive the needle holder, the click hooks thereof is pressed against the conic section and converged and located. Accordingly, the piston stem can drive the needle holder to move rearward and make the click hooks pass through the flange of inner circumference of the barrel so as to retract the needle holder into the barrel.
FIG. 9
shows a conventional safety syringe. The inner circumference of front section of the barrel
81
is formed with a flange
811
. The needle holder
82
fitted in the barrel
81
is formed with a recessed section
821
corresponding to the flange
811
. By means of engagement between the flange
811
and the recessed section
821
, the needle holder
82
can be located in the barrel
81
. The needle holder
82
has an insertion tube
822
for fitting with an injection needle
83
. The inner circumference of the needle holder
82
is formed with two click hooks
823
. The front end of the piston
841
of the piston stem
84
is formed with an engaging section
842
corresponding to the click hooks
823
.
In use, the injection needle
83
is first fitted with the insertion tube
822
of the needle holder
82
. Then, the piston stem
84
is pushed forward to a predetermined position and then pulled rearward so as to suck the medicine into the barrel
81
. After injection, the piston stem
84
is pushed forward to make the engaging section
842
fit into the needle holder
82
. At this time, the click hooks
823
are engaged with the engaging section
842
to prevent the piston stem
84
from departing from the needle holder
82
as shown in FIG.
10
. Accordingly, when pulled rearward, the piston stem
84
can drive the needle holder
82
to move and make the recessed section
821
disengage from the flange
811
. Under such circumstance, the needle holder
82
can be retracted into the barrel
81
along with the piston stem
84
. Accordingly, the injection needle
83
is prevented from protruding outward so as to avoid impalement of medical personnel.
The needle holder
82
is fixed only by means of the engagement between the flange
811
and the recessed section
821
. In the case that the flange
811
more protrudes from the inner circumference of the barrel
81
, the flange
811
will be able to more tightly engage with the recessed section
821
to achieve greater fixing force and prevent the needle holder
82
from moving rearward when inserting the injection needle
83
. However, after the engaging section
842
of the piston stem
84
is engaged into the needle holder
82
, the needle holder
82
will be hard to be driven and retracted into the barrel
81
. In the case that the flange
811
less protrudes from the inner circumference of the barrel
81
, the flange
811
is not so tightly engage with the recessed section
821
and the fixing force is less. Accordingly, after the engaging section
842
of the piston stem
84
is engaged into the needle holder
82
, the needle holder
82
can be easily driven and retracted into the barrel
81
. However, when inserting the injection needle
83
, the needle holder
82
can be hardly truly fixed in the barrel
81
and is likely to be pushed rearward.
Furthermore, when the piston stem
84
is first pushed forward prior to filling of the medicine or bleeding and then pulled rearward to suck the medicine or blood, it often takes place that the engaging section
842
of the piston stem
84
are engaged with the click hooks
823
of the needle holder
82
without departure. Under such circumstance, the syringe must be discarded to use a new syringe. This leads to waste of resource.
SUMMARY OF THE INVENTION
It is therefore a primary object of the present invention to provide a disposable safety syringe. The inner circumference of front end of the barrel of the syringe is formed with a conic section. When the piston stem is forcedly pushed inward to drive the needle holder, the click hooks thereof is pressed against the conic section and converged and located. Accordingly, the piston stem can drive the needle holder to move rearward and make the click hooks pass through the flange of inner circumference of the barrel so as to retract the needle holder into the barrel and ensure safety.
The present invention can be best understood through the following description and accompanying drawings wherein:


REFERENCES:
patent: 3989044 (1976-11-01), Meierhoefer
patent: 4950241 (1990-08-01), Ranford
patent: 5256151 (1993-10-01), Chul
patent: 5531705 (1996-07-01), Alter et al.
patent: 5997511 (1999-12-01), Curie et al.

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