Note: Descriptions are shown in the official language in which they were submitted.
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SAFETY DISPOSABLE SYRINGE
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a safety disposable syringe,
more particularly to a safety disposable syringe
including a barrel and a needle seat provided with a canula
and engageable with a piston on a plunger for withdrawing
the canula into the barrel prior to disposal of the
syringe.
2. Description of the Related Art
Fig. 1 illustrates a conventional safety disposable
syringe that includes a barrel 11, a plunger 14 extending
into the barrel 11, a piston 15 mounted on the plunger
14 and formed with an engaging groove 151, and a needle
seat 13 extending into the barrel 11, connected to a canula
16, and formed with an engaging tongue 131 that is
engageable with the engaging groove 151 so as to permit
withdrawal of the canula 16 into the barrel 11 prior to
disposal of the safety disposable syringe. The needle
seat 13 is formed with a needle channel 133 for extension
of the canula 16 thereinto, and a fluid passage 132
extending from one end of the needle channel 133 through
an end face 1311 of the engaging tongue 131 so as to permit
fluid communication between the canula 16 and a chamber
of the barrel 11. However, since the fluid passage 132
passes through the engaging tongue 131, the latter
requires a larger size to allow formation of the fluid
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passage 132 therethrough. As such, the design of the
aforesaid safety disposable syringe is not suitable for
application to small sized syringes, i.e., syringes that
are less than lcc in size.
SUMMARY OF THE INVENTION
Therefore, the object of the present invention is to
provide a safety disposable syringe that can overcome
the aforesaid drawback associated with the prior art.
According to this invention, a safety disposable
syringe comprises: a barrel having front and rear open
ends and defining a chamber therein and an axis; a plunger
extending through the rear open end and into the chamber
and having a front end; a piston mounted on the front
end of the plunger and formed with a first engaging member;
a canula; and a needle seat extending fittingly through
the front open end of the barrel and having a front end
disposed outwardly of the chamber, and a rear end disposed
in the chamber and having a rear end face facing toward
the piston. The needle seat defines a central channel
extending through the front end of the needle seat for
extension of the canula thereinto, and a fluid passage
extending through the rear end face of the rear end of
the needle seat and in fluid communication with the
central channel and the chamber. The rear end face of
the rear end of the needle seat is formed with a second
engaging member that is axially aligned and that is
engagable with the first engaging member. The fluid
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passage has a first terminating end terminated at the rear end face of the
rear end of
the needle seat, and a second terminating end opposite to the first
terminating end
and terminated at the rear end face of the rear end of the needle seat. The
second
engaging member has a terminating end terminated at the rear end face of the
rear
end of the needle seat and spaced apart from the first terminating end of the
fluid
passage. The needle seat has an outer surface surrounding the axis. The fluid
passage is generally U-shaped and has a radially extending section extending
radially through the outer surface, and two axially extending sections
extending
respectively from two ends of the radially extending section to the first and
second
terminating ends. The fluid passage is indented inwardly and radially from the
outer
surface along an axial length of the outer surface.
In accordance with this invention, there is provided a safety disposable
syringe including: a barrel having front and rear open ends and defining a
chamber
therein and an axis (X), said barrel being formed with an inner shoulder
adjacent to
said front open end; a plunger extending through said rear open end and into
said
chamber, and having a front end; a piston mounted on said front end of said
plunger
and formed with a first engaging member; a cannula; and a needle seat
extending
fittingly through said front open end of said barrel and having a front seat
portion
which has a front end disposed outwardly of said chamber, and which defines a
central channel extending through said front end of said front seat portion
for
extension of said cannula thereinto, and a rear seat portion which is disposed
in said
chamber, and which extends away from said front seat portion to terminate at a
rear
surface confronting said piston; characterized in that said rear seat portion
has an
outer surface that surrounds the axis (X) and that is in frictional contact
with an inner
surface of said front open end of said barrel, said outer surface defining an
annular
retaining groove that is disposed proximate to said front seat portion; said
safety
disposable syringe further including: an engaging flange extending radially
and
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outwardly from said rear surface, and configured to abut against said inner
shoulder
of said barrel axially, said rear seat portion defining a fluid passage having
a radially
extending section that communicates with said central channel, and that
extends
outwardly through said outer surface so as to communicate with said inner
surface of
said front open end of said barrel, said radially extending section being
disposed
below and separated from said annular retaining groove by a partition region
that
borders said radially extending section, and at least one axially extending
section that
is formed in said rear surface adjacent to said engaging flange, that extends
axially
towards said front seat portion and along said outer surface to communicate
with said
radially extending section, and that terminates at said partition region; a
second
engaging member disposed on said rear surface, and axially aligned and
engageable
with said first engaging member; and a sealing ring retained in said retaining
groove
and in sealing contact with said inner surface of said front open end of said
barrel.
BRIEF DESCRIPTION OF THE DRAWINGS
Other features and advantages of the present invention will become
apparent in the following detailed description of the preferred embodiments of
the
invention, with reference to the accompanying drawings, in which:
Fig. 1 is a partly sectional view of a conventional safety disposable
syringe;
Fig. 2 is an exploded perspective view of the first preferred embodiment
of a safety disposable syringe according to this invention;
Fig. 3 is a schematic top view of the first preferred
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embodiment;
Fig. 4 is a fragmentary, partly sectional view of the
first preferred embodiment;
Fig. 5 is a sectional view of a needle seat of the
first preferred embodiment;
Fig. 6 is a fragmentary, partly sectional view
illustrating how a fluid in a barrel is delivered through
a fluid passage and a canula of the first preferred
embodiment;
Fig. 7 is a fragmentary, partly sectional view
illustrating how a piston is brought into engagement with
the needle seat of the first preferred embodiment;
Fig. 8 is a fragmentary, partly sectional view
illustrating how the needle seat together with the canula
is withdrawn into the barrel of the first preferred
embodiment;
Fig. 9 is a fragmentary, partly sectional view
illustrating how a portion of a plunger is removed after
the needle is withdrawn into the barrel of the first
preferred embodiment;
Fig. 10 is a sectional view of the needle seat of the
second preferred embodiment of the safety disposable
syringe according to this invention; and
Fig. 11 is a partly sectional view illustrating a state
where the needle seat together with the canula tilts at
an angle relative to the axis after being withdrawn into
the barrel of the second preferred embodiment.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Before the present invention is described in greater
detail, it should be noted that same reference numerals
have been used to denote like elements throughout the
specification.
Referring to Figs. 2 to 5, the first preferred
embodiment of a safety disposable syringe according to
the present invention is shown to include: a barrel 3
having front and rear open ends 31, 32 and defining a
chamber 30 therein for receiving a medicine and an axis
(X) ; a plunger 5 extending through the rear open end 32
and into the chamber 30 and having a front end 51 formed
with a protrusion 511; a piston 6 mounted on the front
end 51 of the plunger 5 and formed with a rear recess
621 for extension of the protrusion 511 therein, and a
first engaging member 611' opposite to the rear recess
621; a canula 2; and a needle seat 4 extending fittingly
through the front open end 31 of the barrel 3 and having
a front end 41 disposed outwardly of the chamber 30, and
a rear end 42 disposed in the chamber 30 and having a
rear end face 420 facing toward the piston 6. The needle
seat 4 further has an outer surface surrounding the axis
(X) , and defines a central channel 45 extending through
the front end 41 of the needle seat 4 for extension of
the canula 2 thereinto, and a fluid passage 46 extending
through the rear end face 420 of the rear end 42 of the
needle seat 4 and in fluid communication with the central
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channel 45 and the chamber 30. The rear end face 420 of
the rear end 42 of the needle seat 4 is formed with a second
engaging member 44' that is axially aligned and that is
engagable with the first engaging member 611' (see Fig. 7) .
The fluid passage 46 is generally U-shaped, and has a first
terminating end 460 (see Fig. 5) terminated at the rear end
face 420 of the rear end 42 of the needle seat 4, and a
second terminating end 465 opposite to the first
terminating end 460 and terminated at the rear end face
420 of the rear end 42 of the needle seat 4. The second
engaging member 44' has a terminating end 440 (see Fig. 5)
terminated at the rear end face 420 of the rear end 42 of
the needle seat 4 and spaced apart from the first terminating
end 460 of the fluid passage 46. The fluid passage 46 has
a radially extending section 462 extending radially
through the outer surface, and two axially extending
sections 461 extending respectively from two ends of the
radially extending section 462 to the first and second
terminating ends 460, 465. The fluid passage 46 is
indented inwardly and radially from the outer surface
of the needle seat 4 along an axial length of the outer
surface of the needle seat 4.
Preferably, the first and second engaging members 611' ,
44' are engageable with each other in a tongue-and-groove
engaging manner. In this embodiment, the piston 6 is
formed with an engaging groove 611 that defines the first
engaging member 611', and the rear end face 420 of the
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rear end 42 of the needle seat 4 is formed with an engaging
tongue 44 that defines the second engaging member 44'.
Preferably, the volume of the fluid passage 46 is
substantially equal to that of the engaging groove 611
so that when the entire body of the medicine received
in the barrel 3 is driven out, the air trapped in the
engaging groove 611 can be used to drive out residual
medicine retained in the fluid pas sage 46 upon engagement
of the engaging groove 611 with the engaging tongue 44.
This can avoid waste of the medicine from occurring.
In this embodiment, each of the axially extending
sections 461 of the fluid passage 46 has a depth (d) in
a radial direction relative to the axis (X) and a width
(w) in a direction transverse to the radial direction
and the axis (X). The ratio of the width of each of the
axially extending sections 461 of the fluid passage 46
to a perimeter of the rear end 42 of the needle seat 4
is preferably less than 1/15. The ratio of the depth of
each of the axially extending sections 461 of the fluid
passage 46 to a diameter of the rear end 42 of the needle
seat 4 is preferably less than 1/7. In this embodiment,
the width of each of the axially extending sections 461
of the fluid passage 46 is 0.5mm, and the depth of each
of the axially extending sections 461 of the fluid passage
46 is 0.5mm.
In this embodiment, the needle seat 4 is in the form
of a single piece. The engaging tongue 44 extends along
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the axis (X) of the barrel 3. The first and second
terminating ends 460, 465 of the fluid passage 46 are
disposed at two sides of the engaging tongue 44.
The front end 41 of the needle seat 4 has a front end
face 410. The central channel 45 has a first section 451
extending from the front end face 410 of the front end
41 of the needle seat 4, a second section 452 extending
from the first section 451, a third section 453 extending
from the second section 452, and a fourth section 454
extending from the third section 453 to the fluid passage
46. The first section 451 converges in dimensions from
the front end face 410 of the front end 41 of the needle
seat 4 to an adjacent end of the second section 452. The
second section 4 52 diverges in dimensions from an adj acent
end of the first section 451 to an adjacent end of the
third section 453 so as to form a constriction 455 between
the first and second sections 451, 452 for constricting
the canula 2. A glue 8 fills the first section 451 of
the central channel 45 to fix the canula 2 to the needle
seat 4. The rear end 42 of the needle seat 4 is formed
with a neck 421. The barrel 3 is formed with an inner
shoulder 3111 disposed adjacent to the front open end
31 of the barrel 3 and abutting against the neck 421 of
the rear end 42 of the needle seat 4 so as to prevent
undesired removal of the needle seat 4 through the front
open end 31 of the barrel 3.
The needle seat 4 has a tubular wall 40 (see Figs.
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2 and 5) that defines the central channel 45 therein,
a plurality of angularly displaced fins 43 radiating from
an outer surface of the tubular wall 40 and in frictional
contact with an inner surface of the front open end 31
of the barrel 3, and an annular flange 471 connected to
ends of the fins 43. The needle seat 4 is formed with
an annular retaining groove 431 between the annular flange
471 and the radially extending section 462 of the fluid
passage 46. A sealing ring 47 is retained in the retaining
groove 431, and is in sealing contact with the inner
surface of the front open end 31 of the barrel 3.
The barrel 3 has a rear end portion having an inner
surface that has a cylindrical rear segment 321 extending
from the rear open end 32 of the barrel 3, a middle segment
323, and a transition segment 322 interconnecting the
rear segment 321 and the middle segment 323 and diverging
in cross-section from the rear segment 321 to the middle
segment 323. The plunger 5 further has a rear end 52,
and is formed with an annular notch 513 disposed between
the front and rear ends 51, 52 of the plunger 5, a first
annular flange 512 axially spaced apart from the annular
notch 513, and a second annular flange 512' disposed
between the annular notch 513 and the first annular flange
512. The annular notch 513 is disposed between the second
annular flange 512' and the rear end 52 of the plunger
5. The second annular flange 512' has a diameter
substantially equal to that of the rear segment 321 of
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the barrel 3. The first annular flange 512 has a diameter
substantially equal to that of the transition segment
322 of the barrel 3.
Referring to Figs. 6 to 8, in operation, a fluid 9
in the barrel 3 is pushed by an external force acting
on the plunger 5, and passes through the fluid passage
46 and the canula 2 for injection into a patient. When
the engaging groove 611 in the piston 6 is brought into
full engagement with the engaging tongue 44, the fluid
9 in the barrel 3 is completely expelled therefrom, as
best illustrated in Fig. 7. When the safety disposable
syringe is to be discarded after use, the plunger 5 is
pulled back so as to withdraw the needle seat 4 together
with the canula 2 into the barrel 3, as best illustrated
in Fig. 8. When the first annular flange 512 of the plunger
5 is brought into abutment against the transition segment
322 of the inner surface of the rear end portion of the
barrel 3, further rearward movement of the plunger 5 is
prevented. At this state, the annular notch 513 is
substantially flush with a rear end face 320 of the barrel
3, thereby permitting breaking of the plunger 5 at the
annular notch 513 (see Fig. 9).
Figs. 10 and 11 illustrate the second preferred
embodiment of the safety disposable syringe according
to this invention. The second preferred embodiment
differs from the previous embodiment in that the engaging
tongue 44 is tilted relative to the axis (X) of the barrel
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3, while the engaging groove 611 extends along the axis
(X) of the barrel 3.
As illustrated in the preferred embodiments, by
forming the fluid passage 46 in the needle seat 4 such
that it does not pass through the second engaging member
44' (i.e., the engaging tongue 44 formed on the rear end
face 420 of the rear end 42 of the needle seat 4), the
size of the second engaging member 44' can be kept as
small as possible as long as engagement between the first
and second engaging members 611', 44' is sufficient to
permit withdrawal of the needle seat 4 into the barrel
3 by the plunger 5, thereby eliminating the aforesaid
drawback associated with the prior art.
While the present invention has been described in
connection with what are considered the most practical
and preferred embodiments, it is understood that this
invention is not limited to the disclosed embodiments
but is intended to cover various arrangements included
within the scope of the claims.
