Abstrict A disposable syringe includes a barrel having a retaining region
to retain a needle seat for carrying a needle cannula, and a friction
diminishing region extending forwardly from the retaining region
and terminating at a shoulder abutment, a plunger movable in the
barrel toward the needle seat, and a coupling member biased by a
biasing member and having a retained portion to frictionally engage
the plunger, and an anchored portion to engage an anchoring portion
of the needle seat such that when the needle seat is moved past
the friction diminishing region to abut against the shoulder abutment,
a subsequent pushing force applied to the plunger results in release
of the retained portion from the plunger, thereby enabling the anchored
portion to be moved into the plunger by means of the biasing member.
Claims 1. A disposable syringe comprising: a needle cannula; a tubular
needle seat including a front hub portion which is disposed to fix
said needle cannula therein, a gripped portion which extends from
said front hub portion in a longitudinal direction, and a rear anchoring
portion which is disposed opposite to said front hub portion in
the longitudinal direction; a barrel having an inner surrounding
barrel surface which surrounds an axis in the longitudinal direction
and which defines a passage therein, said passage having rearward
and forward openings which are disposed opposite to each other in
the longitudinal direction, said inner surrounding barrel surface
including a larger-diameter portion and a smaller-diameter portion
which are disposed proximate to said rearward and forward openings,
respectively, said larger-diameter portion having a retaining area
which is spaced apart from said smaller-diameter portion in the
longitudinal direction, said smaller-diameter portion including
a retaining region which is disposed proximate to said larger-diameter
portion and which is configured to retain said front hub portion
thereat when said needle seat is in a position of use, and a friction
diminishing region which extends from said retaining region toward
said forward opening and which terminates at a shoulder abutment,
said shoulder abutment defining a communicating hole which permits
passage of said needle cannula therethrough, and being spaced apart
from said front hub portion along the axis in the position of use;
a tubular grip member which, in the position of use, is disposed
to bring said gripped portion into engagement with said retaining
area by virtue of a first frictional force generated therebetween;
a tubular plunger which is disposed to be movable in said passage
along said larger-diameter portion, said plunger having a front
opened end wall which is movable to abut against said grip member,
a rear opened end wall which is disposed opposite to said front
opened end wall and which extends outwardly of said rearward opening
so as to be manually operable, and an intermediate surrounding wall
which is interposed between said front and rear opened end walls
and which defines an accommodation chamber; a coupling member having
a surrounding retained portion which surrounds the axis and which
is disposed in said accommodation chamber to be in frictional engagement
with said intermediate surrounding wall by virtue of a second frictional
force, and an anchored portion which is disposed adjacent to said
front opened end wall in the position of use, which confronts said
rear anchoring portion, and which is engageable with said rear anchoring
portion by a holding force when said coupling member is moved forwardly
towards said forward opening such that, when said grip member is
pushed forward by virtue of forward movement of said plunger against
the first frictional force to cause said front hub portion to move
past said friction diminishing region to abut against said shoulder
abutment, a pushing force subsequently applied to said plunger causes
said anchored portion to rub against said rear anchoring portion,
which remains unmoved in place due to engagement of said front hub
portion with said shoulder abutment, so that said anchored portion
is engaged with said rear anchoring portion and is moved relative
to said intermediate surrounding wall towards said rear opened end
wall so as to release said surrounding retained portion from said
intermediate surrounding wall, thereby enabling said anchored portion
to be moved from the position of use to a retracted position where
said anchored portion is disposed closer to said rear opened end
wall and where said needle seat and said needle cannula are received
in said accommodation chamber; and a biasing member disposed to
bias said anchored portion towards the retracted position.
2. The disposable syringe of claim 1 wherein said passage at said
friction diminishing region has a diameter larger than that of said
passage at said retaining region.
3. The disposable syringe of claim 1 wherein said tubular needle
seat is in form of a metal tube which includes a front segment to
serve as said front hub portion, and a rear segment that is opposite
to said front segment in the longitudinal direction and that has
outer and inner segment surfaces opposite to each other in radial
directions relative to the axis, said outer and inner segment surfaces
being configured to serve as said gripped portion and said rear
anchoring portion, respectively.
4. The disposable syringe of claim 1 wherein said intermediate
surrounding wall of said tubular plunger has a smaller front segment
and a larger rear segment disposed proximate to said front and rear
opened end walls, respectively, and an enlarged terminal segment
disposed between said larger rear segment and said rear opened end
wall.
5. The disposable syringe of claim 4 wherein said enlarged terminal
segment has a vent hole in fluid communication with the ambient
atmosphere.
6. The disposable syringe of claim 5 wherein said coupling member
has a shank portion which extends from said surrounding retained
portion distal from said anchored portion, said biasing member including
a coiled spring which has a front spring end that engages said shank
portion, and a rear spring end that is retained to said rear opened
end wall such that said coiled spring is tensioned when said surrounding
retained portion is in frictional engagement with said intermediate
surrounding wall by virtue of the second frictional force.
7. The disposable syringe of claim 6 wherein said larger rear
segment has an annular rib which is disposed thereon proximate to
said rear opened end wall, said rear spring end of said coiled spring
being retained by said annular rib.
8. The disposable syringe of claim 5 wherein said coupling member
has a shank portion which is interposed between said anchored portion
and said surrounding retained portion, said intermediate surrounding
wall and said shank portion respectively having an annular shoulder
and a flange which are respectively proximate to said front opened
end wall and distal from said anchored portion and which are spaced
apart from each other in the longitudinal direction so as to define
a biasing member receiving space therebetween, said biasing member
being a coiled spring which has front and rear spring ends abutting
against said annular shoulder and said flange, respectively, such
that said coiled spring is compressed when said surrounding retained
portion is in frictional engagement with said intermediate surrounding
wall by virtue of the second frictional force.
9. The disposable syringe of claim 1 wherein said rear anchoring
portion extends rearwardly from said gripped portion along the axis,
said anchored portion having an engaging recess which is configured
to grip said rear anchoring portion with the holding force when
said needle seat is to be placed in the retracted position.
10. The disposable syringe of claim 1 further comprising an end
cap disposed to cover said rear opened end wall, and a seal ring
member which is disposed to establish fluid-tight engagement between
said end cap and said rear opened end wall.
11. The disposable syringe of claim 10 wherein said biasing member
includes a fluid which is contained in said accommodation chamber
at a reduced pressure, and a sealing member which is configured
to provide a sealing between said coupling member and said intermediate
surrounding wall so as to trap said fluid in said accommodation
chamber such that when said surrounding retained portion is released
from said intermediate surrounding wall, said anchored portion is
suctioned to the retracted position due to a pressure difference
between the ambient atmosphere and the reduced pressure.
12. The disposable syringe of claim 11 wherein said sealing member
extends in the longitudinal direction to terminate at a rear end
wall which is disposed rearwardly of said coupling member and which
has a central recess extending inwardly and along the axis so as
to enhance deformability of said rear end wall in radial directions,
thereby enhancing sealing attachment of said sealing member with
said intermediate surrounding wall.
13. The disposable syringe of claim 11 wherein said coupling member
has a shank portion extending rearwardly from said surrounding retained
portion to terminate at an enlarged head portion, said sealing member
being sleeved on said shank portion and being interposed between
said head portion and said surrounding retained portion so as to
be deformed radially for enhancing sealing attachment of said sealing
member with said intermediate surrounding wall.
14. The disposable syringe of claim 11 wherein said sealing member
surrounds the axis, and is formed integrally with said coupling
member.
15. The disposable syringe of claim 11 wherein said sealing member
is formed integrally with said coupling member, is made from a deformable
material, and surrounds said anchored portion, said coupling member
having an annular front edge which is slidable on and is in fluid-tight
engagement with said larger-diameter portion of said inner surrounding
barrel surface.
16. The disposable syringe of claim 1 further comprising a sealing
unit which is in fluid-tight engagement with said friction diminishing
region, said tubular grip member being formed with a deformable
sealing portion which is in fluid-tight engagement with said gripped
portion of said needle seat so as to form a fluid-tight compressible
chamber, said compressible chamber being filled with a fluid, said
front hub portion of said needle seat having a plurality of through
holes formed therethrough so as to be in fluid communication with
said compressible chamber, such that when said tubular grip member
is pushed forwardly by virtue of forward movement of said plunger
to move said front hub portion past said friction diminishing region,
said fluid in said compressible chamber is squeezed through said
through holes, thereby generating a pressure force in the longitudinal
direction that depresses said surrounding gripped portion rearwardly
to help thrust said anchored portion to the retracted position.
17. The disposable syringe of claim 1 wherein said inner surrounding
barrel surface of said barrel further includes an annular shoulder
disposed between said larger-diameter portion and said smaller-diameter
portion, and a plurality of ribs formed on said annular shoulder.
18. The disposable syringe of claim 1 wherein said coupling member
further has a retained shank portion which is disposed between said
surrounding retained portion and said anchored portion and which
extends in said accommodation chamber at said smaller front segment
so as to stabilize said coupling member at said smaller front segment.
Description BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a disposable syringe, more particularly
to a disposable syringe with a friction diminishing means for facilitating
retraction of a needle into a tubular plunger.
[0003] 2. Description of the Related Art
[0004] Conventional syringes, especially those with a sharp needle,
have to be disposed safely after injection. Therefore, there are
many syringes with a retractable needle that is retracted into a
plunger when the plunger reaches the end of its stroke. However,
it is desirable to improve the steady retracted movement of the
syringe and the variety of the diameter of the syringe barrel.
SUMMARY OF THE INVENTION
[0005] The object of the present invention is to provide a disposable
syringe which permits steady retraction of a plunger and which ensures
successful retraction of a needle assembly.
[0006] According to this invention, the disposable syringe includes
a needle cannula, a tubular needle seat, a barrel, a tubular grip
member, a tubular plunger, a coupling member and a biasing member.
[0007] The tubular needle seat includes a front hub portion which
is disposed to fix the needle cannula therein, a gripped portion
which extends from the front hub portion in a longitudinal direction,
and a rear anchoring portion which is disposed opposite to the front
hub portion in the longitudinal direction.
[0008] The barrel has an inner surrounding barrel surface which
surrounds an axis in the longitudinal direction and which defines
a passage therein. The passage has rearward and forward openings
opposite to each other in the longitudinal direction. The inner
surrounding barrel surface includes a larger-diameter portion and
a smaller-diameter portion which are disposed proximate to the rearward
and forward openings, respectively. The larger-diameter portion
has a retaining area which is spaced apart from the smaller-diameter
portion in the longitudinal direction. The smaller-diameter portion
includes a retaining region which is disposed proximate to the larger-diameter
portion and which is configured to retain the front hub portion
thereat when the needle seat is in a position of use, and a friction
diminishing region which extends from the retaining region toward
the forward opening and which terminates at a shoulder abutment.
The shoulder abutment defines a communicating hole which permits
passage of the needle cannula therethrough, and is spaced apart
from the front hub portion along the axis in the position of use.
[0009] The tubular grip member, in the position of use, is disposed
to bring the gripped portion into engagement with the retaining
area by virtue of a first frictional force generated therebetween.
[0010] The tubular plunger is disposed to be movable in the passage
along the larger-diameter portion. The plunger has a front opened
end wall which is movable to abut against the grip member, a rear
opened end wall which is disposed opposite to the front opened end
wall and which extends outwardly of the rearward opening so as to
be manually operable, and an intermediate surrounding wall which
is interposed between the front and rear opened end walls and which
defines an accommodation chamber.
[0011] The coupling member has a surrounding retained portion which
surrounds the axis and which is disposed in the accommodation chamber
to be in frictional engagement with the intermediate surrounding
wall by virtue of a second frictional force, and an anchored portion
which is disposed adjacent to the front opened end wall in the position
of use, which confronts the rear anchoring portion, and which is
engageable with the rear anchoring portion by a holding force when
the coupling member is moved forwardly towards the forward opening.
Thus, when the grip member is pushed by virtue of forward movement
of the plunger against the first frictional force to move the front
hub portion past the friction diminishing region to abut against
the shoulder abutment, a pushing force subsequently applied to the
plunger causes the anchored portion to rub against the rear anchoring
portion, which remains unmoved in place due to engagement of the
front hub portion with the shoulder abutment, so that the anchored
portion is engaged with the rear anchoring portion and is moved
relative to the intermediate surrounding wall towards the rear opened
end wall so as to release the surrounding retained portion from
the intermediate surrounding wall, thereby enabling the anchored
portion to be moved from the position of use to a retracted position
where the anchored portion is disposed closer to the rear opened
end wall, and where the needle seat and the needle cannula are received
in the accommodation chamber.
[0012] The biasing member is disposed to bias the anchored portion
towards the retracted position.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] 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:
[0014] FIG. 1 is an exploded sectional view of the first preferred
embodiment of a disposable syringe according to this invention;
[0015] FIG. 2 is a sectional view of the first preferred embodiment
in a state of use;
[0016] FIGS. 3 to 5 are fragmentary sectional views of the first
preferred embodiment, showing a coupling member in three different
states;
[0017] FIG. 6 is a sectional view of the first preferred embodiment
in a retracted state;
[0018] FIG. 7 is a sectional view of the second preferred embodiment
of a disposable syringe according to this invention;
[0019] FIGS. 8 and 9 are sectional views of the third preferred
embodiment of a disposable syringe according to this invention in
a state of use and in a retracted state, respectively;
[0020] FIG. 10 is a sectional view of the fourth preferred embodiment
of a disposable syringe according to this invention;
[0021] FIG. 11 is a sectional view of the fifth preferred embodiment
of a disposable syringe according to this invention in a state of
use;
[0022] FIG. 12 is a sectional view of the fifth preferred embodiment,
showing the state in which a needle seat passes by a friction diminishing
region;
[0023] FIG. 13 is a sectional view of the fifth preferred embodiment
in a retracted state;
[0024] FIGS. 14 and 15 are sectional views of the sixth and seventh
preferred embodiments of a disposable syringe according to this
invention, respectively;
[0025] FIGS. 16 and 17 are sectional views of the eighth preferred
embodiment of a disposable syringe according to this invention in
a state of use and in a retracted state, respectively;
[0026] FIG. 18 is a sectional view of the ninth preferred embodiment
of a disposable syringe according to this invention in a state of
use;
[0027] FIG. 19 is a fragmentary sectional view of the ninth preferred
embodiment, showing the state in which a needle seat passes by a
friction diminishing region;
[0028] FIG. 20 is a fragmentary sectional view of the tenth preferred
embodiment of a disposable syringe according to this invention in
a state of use;
[0029] FIG. 21 is a sectional view of the tenth preferred embodiment
in a retracted state; and
[0030] FIGS. 22 to 25 are sectional views of the eleventh, twelfth,
thirteenth and fourteenth preferred embodiments of a disposable
syringe according to this invention, respectively.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] 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.
[0032] Referring to FIGS. 1 and 2 the first preferred embodiment
of a disposable syringe according to the present invention is shown
to comprise a needle assembly 2 a barrel 1 a tubular grip member
3 a tubular plunger 4 a coupling member 51 and a biasing member
52.
[0033] The needle assembly 2 includes a needle cannula 22 and a
tubular needle seat 21. The needle seat 21 is in the form of a hard
thin wall tube, such as a metal or carbon fiber tube which includes
a front segment 211 to serve as a front hub portion 211 that is
disposed to fix the needle cannula 22 therein, and a rear segment
that extends from the front segment along an axis (X) in a longitudinal
direction. The rear segment has outer and inner segment surfaces
opposite to each other in radial directions relative to the axis
(X) to serve as a gripped portion 212 and a rear anchoring portion
213 respectively.
[0034] The barrel 1 has an inner surrounding barrel surface 13
which surrounds the axis (X) in the longitudinal direction and which
defines a passage 10 therein. The passage 10 has rearward and forward
openings 132131 which are disposed opposite to each other in the
longitudinal direction. The inner surrounding barrel surface 13
includes a larger-diameter portion 11 and a smaller-diameter portion
12 which are disposed proximate to the rearward and forward openings
132 131 respectively, an annular shoulder 14 which converges gradually
from the larger-diameter portion 11 to the smaller-diameter portion
12 and a plurality of ribs 15 which are formed on an inner surface
of the shoulder 14 to retain a part of the front hub portion 211
of the needle seat 21. The larger-diameter portion 11 has a retaining
area 16 which is in the form of an annular protrusion and which
is spaced apart from the smaller-diameter portion 12 in the longitudinal
direction.
[0035] The smaller-diameter portion 12 includes a retaining region
121 which is disposed in connection with the ribs 15 and which is
configured to retain a part of the front hub portion 211 of the
needle seat 21 thereat when the needle seat 21 is in a position
of use, and a friction diminishing region 122 which extends from
the retaining region 121 toward the forward opening 131 and which
terminates at a shoulder abutment 124. The passage 10 at the friction
diminishing region 122 has a diameter larger than that of the passage
10 at the retaining region 121. The shoulder abutment 124 defines
a communicating hole 123 which is configured to permit passage of
the needle cannula 22 therethrough, and is spaced apart from the
front hub portion 211 along the axis (X) in the position of use.
[0036] In the position of use, the tubular grip member 3 is disposed,
to bring the gripped portion 212 of the needle seat 21 into engagement
with the retaining area 16 by virtue of a first frictional force
generated therebetween. In particular, the grip member 3 is in fluid-tight
and frictional engagement with the retaining area 16 and has an
axially extending hole 31 for receiving the gripped portion 212.
[0037] The tubular plunger 4 is disposed to be movable in the passage
10 along the larger-diameter portion 11. The plunger 4 has a front
opened end wall 421 which is movable to abut against the grip member
3 a rear opened end wall 422 which is disposed opposite to the
front opened end wall 421 and which extends outwardly of the rearward
opening 132 so as to be manually operable, and an intermediate surrounding
wall 42 which is interposed between the front and rear opened end
walls 421422 and which defines an accommodation chamber 41. The
intermediate surrounding wall 42 has a smaller front segment 423
and a larger rear segment 424 disposed proximate to the front and
rear opened end walls 421422 respectively, to form a shoulder
426 therebetween. An enlarged terminal segment 425 is disposed between
the larger rear segment 424 and the rear opened end wall 422 and
is formed with a vent hole 429 so as to be in fluid communication
with the ambient atmosphere. An annular rib 428 is disposed between
the larger rear segment 424 and the enlarged terminal segment 425
and extends in the longitudinal direction. An end cap 44 is disposed
to cover the rear opened end wall 422 and has an annular groove
441 for engagement with the enlarged terminal segment 425. In addition,
an annular groove 427 is formed in an inner peripheral surface of
the larger rear segment 424 proximate to the shoulder 426. A seal
ring 43 which is made of a deformable material, is sleeved retainingly
over an outer peripheral surface of the smaller front segment 423
so as to be slidable on and to be in fluid-tight frictional engagement
with both the larger-diameter portion 11 of the inner surrounding
barrel surface 13 and the coupling member 51.
[0038] The coupling member 51 has a surrounding retained portion
512 which surrounds the axis (X) and which is in the form of an
annular protrusion disposed to be in frictional engagement with
the annular groove 427 in the intermediate surrounding wall 42 by
virtue of a second frictional force, an anchored portion 514 which
extends forwardly of the front opened end wall 421 in the position
of use to confront the rear anchoring portion 213 so as to be engageable
with the rear anchoring portion 213 by a holding force when the
coupling member 51 is moved forwardly towards the forward opening
131 a retained shank portion 513 which is disposed between the
surrounding retained portion 512 and the anchored portion 514 and
which extends in the accommodation chamber 41 at the smaller front
segment 423 so as to stabilize the coupling member 51 at the smaller
front segment 423 and a shank portion 511 which extends from the
surrounding retained portion 512 distal from the anchored portion
514.
[0039] The biasing member 52 is a coiled spring, and has a front
spring end 521 which engages the shank portion 511 and a rear spring
end 522 which is retained between the annular rib 428 and the intermediate
surrounding wall 42 such that the coiled spring 52 is tensioned
when the surrounding retained portion 512 is in frictional engagement
with the annular groove 427 by virtue of the second frictional force,
as shown in FIG. 2.
[0040] After completion of an injection course, the plunger 4 is
pressed forwardly by a pushing force to permit abutment of the seal
ring 43 against the grip member 3. At this time, the anchored portion
514 is extended into the axially extending hole 31. Subsequently,
with reference to FIGS. 3 and 4 a manual pushing force is further
applied to the plunger 4 to push the grip member 3 forward against
the first frictional force (i.e., the frictional engagement between
the grip member 3 and the retaining area 16) such that the anchored
portion 514 is partially extended into and engaged with the rear
anchoring portion 213 and such that the front hub portion 211 moves
past the friction diminishing region 122 to abut against the shoulder
abutment 124. Meanwhile, the movement of the front hub portion 211
past the friction diminishing region 122 results in reduced friction
therebetween. Therefore, as shown in FIG. 5 when a pushing force
is subsequently applied to the plunger 4 to cause the anchored portion
514 to rub against the rear anchoring portion 213 which remains
unmoved due to engagement of the front hub portion 211 with the
shoulder abutment 124 the anchored portion 514 is engaged with
the rear anchoring portion 213 and is moved relative to the intermediate
surrounding wall 42 towards the rear opened end wall 422 so as to
release the surrounding retained portion 512 from the annular groove
427 in the intermediate surrounding wall 42 thereby enabling the
anchored portion 514 to be moved by the biasing force of the coiled
spring 52 from the position of use to a retracted position where
the anchored portion 514 is disposed closer to the rear opened end
wall 422 and where the needle assembly 2 (i.e. the needle seat 21
and the needle cannula 22) is received in the accommodation chamber
41 as shown in FIG. 6.
[0041] It is noted that with the provision of the friction diminishing
region 122 which provides a space of triggering action for retraction
of the needle assembly 2 the front hub portion 211 can be pushed
forwards relative to the smaller-diameter portion 12 so that the
friction between the front hub portion 211 and the smaller-diameter
portion 12 to be overcome in the course of retraction of the needle
assembly 2 into the accommodation chamber 41 by the coiled spring
52 can be reduced. In other words, the substantially continuing
forward movement of the needle seat 21 relative to the smaller-diameter
portion 12 after the injection course and its subsequently rearward
movement due to retraction of the needle assembly 2 by the coiled
spring 52 transform the static friction between the front hub portion
211 and the smaller-diameter portion 12 into a kinetic friction,
which can be easily overcome by the predetermined biasing force
of the coiled spring 52 in the course of retraction of the needle
assembly 2 into the accommodation chamber 41 thereby ensuring successful
and smooth retraction of the needle assembly 2.
[0042] It is further noted that since the needle seat 21 is in
the form of a metal tube, it can be configured to have a relatively
small diameter. Thus, the needle cannula 22 can be formed to have
a relatively small diameter, as shown in FIGS. 1 to 5 so as to
be adapted for injecting medication of a very small volume, such
as 1 ml. Likewise, the barrel 1 can be configured to have a smaller
diameter with a relatively compensatory elongation of the length
of the barrel for a unit medication volume. Thus, the spacing of
graduations (not shown) marked on the barrel 1 of extremely small
volume, such as 1 cc., and smaller ones, can be relatively large
to facilitate accurate reading of the volume of medication in injection
course.
[0043]
[0044] Referring to FIG. 7 the second preferred embodiment of
a disposable syringe according to this invention is similar to the
first preferred embodiment in construction, but is adapted for injecting
medication of a general volume, such as 3 ml, 5 ml, or more. That
is, the barrel 1 the tubular plunger 4 and the tubular needle seat
21 have relatively large diameters. The tubular needle seat 21 is
in the form of a plastic injecting tube, and has a rear anchoring
portion 213 which extends rearwardly from the gripped portion 212
along the axis (X). In addition, the coupling member 51 has an anchored
portion 514 which has an engaging recess 516 that is configured
to grip the rear anchoring portion 213 with a holding force when
the needle seat 21 is placed in the retracted position.
[0045] Referring to FIGS. 8 and 9 the third preferred embodiment
of a disposable syringe according to this invention is similar to
the first preferred embodiment in construction, except that the
coupling member 51 has a shank portion 511 which is interposed between
the anchored portion 514 and the surrounding retained portion 512.
In addition, the intermediate surrounding wall 42 of the tubular
plunger 4 and the shank portion 511 respectively have an annular
shoulder 426 and a flange 515 which are respectively proximate to
the front opened end wall 421 of the plunger 4 and distal from the
anchored portion 514 and which are spaced apart from each other
in the longitudinal direction so as to define a biasing member receiving
space therebetween. The biasing member 54 is a coiled spring which
has front and rear spring ends 541542 abutting against the annular
shoulder 426 and the flange 515 respectively, such that the coiled
spring is compressed when the surrounding retained portion 512 is
in frictional engagement with the annular groove 427 in the intermediate
surrounding wall 42 by virtue of the second frictional force.
[0046] Referring to FIG. 10 the fourth preferred embodiment of
a disposable syringe according to this invention is similar to the
third preferred embodiment in construction, but is adapted for injecting
medication of a general volume, such as 3 ml, 5 ml, or more. That
is, the barrel 1 the tubular plunger 4 and the tubular needle seat
21 have relatively larger diameters. The tubular needle seat 21
is in the form of a plastic injecting tube, and has a rear anchoring
portion 213 which extends rearwardly from the gripped portion 212
along the axis (X). In addition, the coupling member 51 has an anchored
portion 514 which has an engaging recess 516 which is configured
to grip the rear anchoring portion 213 with a holding force when
the needle seat 21 is placed in the retracted position.
[0047] Referring to FIGS. 11 to 13 the fifth preferred embodiment
of a disposable syringe according to this invention is similar to
the first preferred embodiment in construction. The difference resides
in that a seal ring member 45 such as an O-ring, is disposed between
the rear opened end wall 422 and the annular groove 441 in the end
cap 44 to establish fluid-tight engagement therebetween. The enlarged
terminal segment 425 is not formed with the vent hole described
in the first preferred embodiment. In addition, instead of the coiled
spring 5254 described above, the biasing member includes a fluid,
such as air, which is contained in the accommodation chamber 41
in the tubular plunger 4 at a relatively reduced pressure, and a
sealing member 55 which is sleeved on the shank portion 511 of the
coupling member 51 to provide a seal between the coupling member
51 and the intermediate surrounding wall 42 so as to trap the fluid
in the accommodation chamber 41. Thus, when the surrounding retained
portion 512 is released from the intermediate surrounding wall 42
the anchored portion 514 is suctioned to the retracted position
due to a pressure difference between the ambient atmosphere and
the reduced pressure.
[0048] Further, referring to FIG. 14 in the sixth preferred embodiment
of a disposable syringe according to this invention, which is similar
to the fifth preferred embodiment, the sealing member 55 extends
in the longitudinal direction to terminate at a rear end wall 550
which is disposed rearwardly of the coupling member 51 and which
has a central recess 551 extending inwardly and along the axis (X)
so as to enhance deformability of the rear end wall 550 in radial
directions, thereby enhancing sealing attachment of the sealing
member 55 with the intermediate surrounding wall 42.
[0049] Referring to FIG. 15 the seventh preferred embodiment of
a disposable syringe according to this invention is similar to the
fifth preferred embodiment in construction, but is adapted for injecting
medication of a general volume, such as 3 ml, 5 ml, or more. The
tubular needle seat 21 is in the form of a plastic injecting tube,
and has a rear anchoring portion 213 which extends rearwardly from
the gripped portion 212 along the axis (X) so as to engage an engaging
recess 516 in the anchored portion 514 of the coupling member 51
with a holding force when the needle seat 21 is placed in the retracted
position. In addition, the coupling member 51 has a shank portion
511 extending rearwardly from the surrounding retained portion 512
to terminate at an enlarged head portion 519. The sealing member
55 is sleeved on the shank portion 511 and is interposed between
the head portion 519 and the surrounding retained portion 512 so
as to be deformed radially for enhancing the sealing attachment
with the intermediate surrounding wall 42.
[0050] Referring to FIGS. 16 and 17 the eighth preferred embodiment
of a disposable syringe according to this invention is similar to
the seventh preferred embodiment in construction, and is adapted
for injecting medication of a general volume, such as 3 ml, 5 ml,
or more. In this embodiment, the larger rear segment 424 of the
intermediate surrounding wall 42 of the tubular plunger 4 includes
front and rear wall segments 42414242 which are disposed proximate
to the front and rear opened end walls 421422 respectively, and
which have smaller and larger outer peripheral surfaces, respectively.
The plunger 4 further includes a plurality of rib fins 46 which
are formed on the smaller outer peripheral surface of the front
wall segment 4241 and which are flush with the larger outer peripheral
surface of the rear wall segment 4242 so as to guide movement of
the plunger 4 relative to the larger-diameter portion 11 of the
inner surrounding barrel surface 13 while minimizing frictional
force therebetween. The smaller front segment 423 and the coupling
member 51 respectively have an annular protrusion 427a and an annular
groove 512a which engage each other to provide the second frictional
force. The coupling member 51 further has a tapered rear portion
517 opposite to the engaging recess 516 so as to establish fluid-tight
engagement with the smaller front segment 423. The sealing member
55 is formed integrally with the coupling member 51 and is disposed
between the tapered rear portion 517 and the annular groove 512a.
[0051] When the surrounding retained portion (the annular groove
512a) is released from the intermediate surrounding wall 42 (the
annular protrusion 427a), the coupling member 51 is received in
the accommodation chamber 41 at the front wall segment 4241 and
is held in fluid-tight contact with the front wall segment 4241
thereby facilitating sliding of the coupling member 51 as well
as the needle assembly 2 to the retracted position.
[0052] Referring to FIGS. 18 and 19 the ninth preferred embodiment
of a disposable syringe according to this invention is similar to
the eighth preferred embodiment in construction, but is adapted
for injecting medication of an extremely small injection volume,
such as 1 ml. The sealing member 55 is formed integrally with the
coupling member 51 is made from a deformable material, and surrounds
the anchored portion 514. In addition, the coupling member 51 has
an annular front edge 518 which is slidable on and is in fluid-tight
engagement with the larger-diameter portion 11 of the barrel 1 so
as to serve as the seal ring 43 in the previous preferred embodiment.
When the coupling member 51 is placed in the retracted position,
the annular front edge 518 is deformed and converged to be retracted
into the accommodation chamber 41.
[0053] Referring to FIGS. 20 and 21 the tenth preferred embodiment
of a disposable syringe according to this invention is similar to
the eighth preferred embodiment in construction. In this embodiment,
a sealing unit 7 is further disposed to be in fluid-tight engagement
with the friction diminishing region 122 and is spaced apart from
the shoulder abutment 124 to define a space of triggering action
for retraction of the needle assembly 2. The sealing unit 7 includes
an elastomeric plug 71 and a ring plate 72 abutting against each
other. The tubular grip member 3 is formed with a deformable sealing
portion 32 which is in fluid-tight engagement with the gripped portion
212 of the needle seat 21 so as to form a fluid-tight compressible
chamber 73. The compressible chamber 73 is filled with a fluid.
The front hub portion 211 of the needle seat 21 is disposed to abut
against the sealing unit 7 and has a plurality of through holes
214 formed therethrough so as to be in fluid communication with
the compressible chamber 73. Thus, when the tubular grip member
3 is pushed forwardly by virtue of forward movement of the plunger
4 to move the front hub portion 211 past the friction diminishing
region 122 the fluid in the compressible chamber 73 is squeezed
through the through holes 214 thereby generating a pressure force
in the longitudinal direction that depresses the surrounding gripped
portion 212 rearwardly to help thrust the anchored portion 514 rearward
to the retracted position.
[0054] Referring to FIGS. 22 to 25 the eleventh, twelfth, thirteenth
and fourteenth preferred embodiments of a disposable syringe according
to this invention are respectively similar to the ninth, second,
fourth and sixth preferred embodiments in construction. Besides,
in each of these embodiments, the disposable syringe further comprises
a sealing unit 7 which is the same as that of the tenth preferred
embodiment, and which is disposed to be in fluid-tight engagement
with the friction diminishing region 122.
[0055] While the present invention has been described in connection
with what is 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 spirit and scope of the broadest interpretations and
equivalent arrangements.
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