Abstrict A disposable syringe has a needle seat with an upper segment adapted
to be sleeved over by a needle unit, and a lower segment retained
in a passage of a barrel. A plunger has a stem portion movable in
the passage, a surrounding engaging portion in sealing contact with
the passage so as to be moved by the stem portion of the plunger
in a position of use, and a head which is moved towards and is held
by a grip segment in the needle seat when the surrounding engaging
portion is depressed by an edge portion of the needle seat by virtue
of a continuing depression force of the plunger, thereby permitting
the needle seat to be brought into the passage for safe disposal.
Claims We claim:
1. A disposable syringe adapted to be used with a needle unit which
includes a needle hub and a needle securely affixed to the needle
hub, said syringe comprising: a barrel having an inner surrounding
barrel wall surface which surrounds an axis and which confines a
passage, said passage having lower and upper open ends which are
disposed opposite to each other in a longitudinal direction parallel
to the axis, said inner surrounding barrel wall surface including
a larger-diameter segment and a smaller-diameter segment which are
disposed proximate to said lower and upper open ends, respectively,
and which cooperatively form a first surrounding shoulder portion
therebetween, the smaller-diameter segment including a retaining
groove defined therein; a tubular needle seat disposed to be insertable
into said passage from said lower open end toward said upper open
end, said needle seat including a protruding lower surrounding edge
portion which is disposed to abut against said first surrounding
shoulder portion, an upper surrounding edge portion disposed opposite
to said lower surrounding edge portion in the longitudinal direction,
and a surrounding seat wall interposed between said lower and upper
surrounding edge portions, and having an inner tubular wall surface
which surrounds the axis to confine a duct and which has a grip
segment, and an outer tubular wall surface which includes a lower
segment including a retaining protrusion defined thereon and proximate
to said lower surrounding edge portion, lower segment being configured
such that, when said upper surrounding edge portion is forced to
extend outwardly of said upper open end after said tubular needle
seat is inserted into said passage, said lower segment will be brought
to a position of use, where said lower segment engages and is retained
at said smaller-diameter segment by virtue of a first friction force
generated by retaining engagement of the retaining protrusion in
the retaining groove while said protruding lower surrounding edge
portion abuts against said first surrounding shoulder portion, the
lower segment being further configured such that, when said upper
surrounding edge portion is forced against the first friction force
so as to be retracted into said passage via said upper open end,
said upper surrounding edge portion will be brought to a retracted
position, where said lower segment and said protruding lower surrounding
edge portion are remote from said smaller-diameter segment and said
first surrounding shoulder portion, respectively, and an upper segment
disposed opposite to said lower segment and proximate to said upper
surrounding edge portion, said upper segment being adapted to be
sleeved over by the needle hub so as to communicate said duct with
the needle hub; and a plunger including a stem portion which is
disposed to be movable in said passage of said barrel and which
has inner and outer segments opposite to each other in the longitudinal
direction, said outer segment extending outwardly of said lower
open end, an actuated end extending from said outer segment so as
to be actuated to move said stem portion along said passage, a surrounding
engaging portion which is disposed to be retainingly sleeved on
said inner segment by virtue of a second friction force, and which
in sealing contact with and which is slidable relative to said larger-diameter
segment so as to be moved with said stem portion in the position
of use, and a head disposed to extend from said inner segment toward
said grip segment, and configured such that, when said surrounding
engaging portion is brought by said inner segment to engage said
lower surrounding edge portion and is depressed by said lower surrounding
edge portion by virtue of a third force generated as a consequence
of continuing movement of said inner segment towards said smaller-diameter
segment, the third force being greater than the second friction
force such that said surrounding engaging portion is blocked by
said lower surrounding edge portion to thereby permit said head
to move towards said grip segment of said tubular needle seat and
to be held by virtue of a fourth friction force that is greater
than the first friction force while said lower segment remains engaged
and unmoved relative to said smaller-diameter segment.
2. The disposable syringe of claim 1 wherein one of said lower
segment and said smaller-diameter segment is formed with a retaining
groove, and the other one of said lower segment and said smaller-diameter
segment is formed with a retaining protrusion which engages retainingly
said retaining groove when said lower segment is in the position
of use so as to generate the first friction force.
3. The disposable syringe of claim 1 wherein said grip segment
has a concave portion which extends inwardly from said inner tubular
wall surface in radial directions relative to the axis to form a
second surrounding shoulder portion that is adjacent to said lower
surrounding edge portion, said head having a surrounding abutting
portion which is configured so as to be insertable into said concave
portion and to abut against said second surrounding shoulder portion,
thereby generating the fourth friction force to bring said upper
surrounding edge portion to the retracted position.
4. The disposable syringe of claim 3 wherein said head further
has a spindle portion which extends from said surrounding abutting
portion along the axis and which terminates at two split halves
that are spaced apart from each other in a direction transverse
to the longitudinal direction, said split halves respectively having
two upper terminal anchoring edges which are remote from said surrounding
abutting portion and which are configured such that said split halves
are pressed by said inner tubular wall surface to move towards each
other against a biasing action when said split halves are moved
towards said upper surrounding edge portion, and such that said
upper terminal anchoring edges engage said upper surrounding edge
portion once said split halves are moved beyond said upper surrounding
edge portion.
5. The disposable syringe of claim 4 wherein said inner tubular
wall surface has a diameter which gradually decreases from said
lower surrounding edge portion to said upper surrounding edge portion,
said spindle portion having an outer diameter which gradually decreases
from said surrounding abutting portion to said split halves.
6. The disposable syringe of claim 3 wherein said surrounding
abutting portion is configured to be substantially hollow so as
to provide a greater flexibility.
7. The disposable syringe of claim 1 wherein said surrounding
engaging portion is made of a deformable material, and has upper
and lower end faces opposite to each other in the longitudinal direction
and proximate to and distal from said lower surrounding edge portion,
respectively, and an outer surrounding surface disposed between
said upper and lower end faces and concaved toward the axis.
8. The disposable syringe of claim 1 wherein said lower surrounding
edge portion has an upper edge surface which abuts against said
first surrounding shoulder portion when said lower segment is in
the position of use, and a lower edge surface for abutment and depression
by said surrounding engaging portion.
9. The disposable syringe of claim 1 further comprising a spline
member disposed between said smaller-diameter segment and said lower
segment to prevent relative rotation therebetween.
10. The disposable syringe of claim 1 further comprising a protruding
ring which is disposed on and which projects inwardly and radially
from said larger-diameter segment adjacent to said lower open end,
and a surrounding flange which is disposed to surround said inner
segment adjacent to said head and which is engageable with said
protruding ring.
11. The disposable syringe of claim 10 wherein said inner segment
has a weakening area which is disposed proximate to said surrounding
flange such that when said surrounding flange is brought to engage
said protruding ring, said weakening area extends outwardly of said
lower open end so as to ease breaking of said stem portion off said
plunger at said weakening area.
Description BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a disposable syringe, more particularly
to a disposable syringe which enables a needle unit to be retracted
within a barrel after use for safe disposal and use.
2. Description of the Related Art
Referring to FIG. 1 a conventional disposable syringe assembly
10 is shown to include a barrel 11 a plunger 12 and a needle unit
13. The barrel 11 has an open neck end portion 111 to which a needle
hub 131 of the needle unit 13 is attached, and an open rear end
from which the plunger 12 is slidably inserted into the barrel 11.
A forward end 121 of the plunger 12 is snugly fitted against, but
is nevertheless slidable along, the inner surface of the barrel
11 through a distance (L). The needle unit 13 further has a needle
132 extending from the needle hub 131 and a cap 133 with an open
end which is fitted around an outer edge of the needle hub 131
with the needle 132 enclosed within the cap 133. The cap 133 is
removed from the needle hub 131 when the syringe assembly 10 is
to be used, and is sleeved back after use to ensure that the needle
132 is covered. Thereafter, the needle unit 13 is detached from
the barrel 11 along with the cap 133 covering the needle 132.
However, the medical or nursing personnel who has to handle the
conventional disposable syringe assembly 10 is exposed to the risk
of being pricked by the needle 132 when sleeving the cap 133 back
on the needle hub 131 after using the disposable syringe assembly
10 since the dimension of the open end of the cap 133 is small.
Moreover, as forward movement of the forward end 121 of the plunger
12 terminates at the point (P1), some medicine or blood may remain
within the neck end portion 111 which may cause contamination to
the personnel who is unfortunately pricked by the needle 132.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a disposable syringe
which provides greater safety in use and which eliminates the aforesaid
drawback of the prior art.
According to this invention, the disposable syringe includes a
barrel having an inner surrounding barrel wall surface which surrounds
an axis and which confines a passage. The passage has lower and
upper open ends disposed opposite to each other in a longitudinal
direction parallel to the axis. The inner surrounding barrel wall
surface includes a larger-diameter segment and a smaller-diameter
segment which are disposed proximate to the lower and upper open
ends, respectively, and which cooperatively form a surrounding shoulder
portion therebetween.
A tubular needle seat is insertable into the passage from the lower
open end toward the upper open end, and includes a lower surrounding
edge portion disposed to abut against the first surrounding shoulder
portion, an upper surrounding edge portion disposed opposite to
the lower surrounding edge portion in the longitudinal direction,
and a surrounding seat wall interposed therebetween. The surrounding
seat wall has an inner tubular wall surface which surrounds the
axis to confine a duct which forms a grip segment, and an outer
tubular wall surface. The outer tubular wall surface includes a
lower segment proximate to the lower surrounding edge portion, and
an upper segment disposed opposite to the lower segment and proximate
to the upper surrounding edge portion. When the upper surrounding
edge portion is forced to extend outwardly of the upper open end
after the tubular needle seat is inserted into the passage, the
lower segment will be brought to a position of use, where the lower
segment engages and is retained at the smaller-diameter segment
by virtue of a first friction force generated therebetween while
the lower surrounding edge portion abuts against the surrounding
shoulder portion. In addition, when the upper surrounding edge portion
is forced against the first friction force so as to be retracted
into the passage via the upper open end, the upper surrounding edge
portion will be brought to a retracted position, where the lower
segment and the surrounding lower edge portion are remote from the
smaller-diameter segment and the first surrounding shoulder portion,
respectively. The outer tubular wall surface is adapted to be sleeved
over by a needle hub of a needle unit so as to communicate the duct
with the needle hub.
A plunger includes a stem portion which is disposed to be movable
in the passage and which has inner and outer segments opposite to
each other in the longitudinal direction. The outer segment extends
outwardly of the lower open end of the passage. An actuated end
extends from the outer segment so as to be actuated to move the
stem portion along the passage. A surrounding engaging portion is
retainingly sleeved on the inner segment by virtue of a second friction
force, and is in sealing contact with and is slidable relative to
the larger-diameter segment so as to be moved with the stem portion
in the position of use. A head extends from the inner segment toward
the grip segment. When the surrounding engaging portion is brought
by the inner segment to engage the lower surrounding edge portion
and is depressed by the lower surrounding edge portion by virtue
of a third force generated as a consequence of continuing movement
of the inner segment towards the smaller-diameter segment, the third
force is greater than the second friction force such that the surrounding
engaging portion is retained by the lower surrounding edge portion
to thereby permit the head to move towards the grip segment of the
tubular needle seat and to be held by virtue of a fourth friction
force that is greater than the first friction force.
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 longitudinal cross-sectional view of a conventional
disposable syringe assembly;
FIG. 2 is an exploded perspective view of a first preferred embodiment
of a syringe according to this invention for use with a needle unit
to form a syringe assembly;
FIG. 3 is a perspective view of the syringe assembly according
to the first preferred embodiment;
FIG. 4 is a longitudinal cross-sectional view showing the syringe
assembly during use;
FIG. 5 is a longitudinal cross-sectional view showing the syringe
assembly in a state of use;
FIG. 6 is a longitudinal cross-sectional view showing the syringe
assembly in a state in which a head of a plunger is held by a grip
segment of a needle seat;
FIG. 7 is a longitudinal cross-sectional view showing the syringe
assembly in a retracted state;
FIG. 8 is a longitudinal cross-sectional view showing a second
preferred embodiment of a disposable syringe according to this invention
for use with a needle unit to form a syringe assembly;
FIG. 9 is a longitudinal cross-sectional view showing the syringe
assembly according to the second preferred embodiment in a state
in which a head of a plunger is held by a grip segment of a needle
seat; and
FIG. 10 is a longitudinal cross-sectional view showing the syringe
assembly in a retracted state.
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 3 and 4 the first preferred embodiment of
the disposable syringe according to the present invention is shown
to be used with a needle unit 40 to form a syringe assembly. The
needle unit 40 includes a needle hub 42 and a needle 41 which is
securely affixed to the needle hub 42. The syringe in this embodiment
is shown to comprise a barrel 20 a tubular needle seat 30 and
a plunger 50.
The barrel 20 has an inner surrounding barrel wall surface 221
which surrounds an axis X and which confines a passage 21. The passage
21 has lower and upper open ends 211 212 which are disposed opposite
to each other in a longitudinal direction parallel to the axis X.
The inner surrounding barrel wall surface 221 includes a larger-diameter
segment 213 and a smaller-diameter segment 214 which are disposed
proximate to the lower and upper open ends 211 212 respectively,
and which cooperatively form a first surrounding shoulder portion
215 therebetween. A finger flange 23 is disposed on an outer surrounding
barrel wall surface 222 of the barrel 20 at the lower open end 211.
The smaller-diameter segment 214 is formed with a retaining groove
223 proximate to the first surrounding shoulder portion 215 and
an axially extending friction spline portion 216 remote from the
first surrounding shoulder portion 215. A protruding ring 217 is
formed on and projects inwardly and radially from the larger-diameter
segment 213 adjacent to the lower open end 211.
The tubular needle seat 30 is disposed to be insertable into the
passage 21 from the lower open end 211 toward the upper open end
212. The needle seat 30 includes a lower surrounding edge portion
33 disposed to abut against the first surrounding shoulder portion
215 and having an outer surrounding surface 333 which abuts sealingly
against the larger-diameter segment 213 an upper surrounding edge
portion 321 disposed opposite to the lower surrounding edge portion
33 in the longitudinal direction, and a surrounding seat wall 32
interposed therebetween.
The seat wall 32 has an inner tubular wall surface 324 which surrounds
the axis X to confine a duct 31. The duct 31 has a diameter that
gradually decreases from the lower surrounding edge portion 33 to
the upper surrounding edge portion 321. The inner tubular wall surface
324 forms a grip segment. In this embodiment, the grip segment includes
a concave portion 326 which extends inwardly from the inner tubular
wall surface 324 in radial directions relative to the axis X to
form a second surrounding shoulder portion 329 that is adjacent
to the lower surrounding edge portion 33.
The seat wall 32 further has an outer tubular wall surface 325
which includes lower and upper segments 322 323. The lower segment
322 is proximate to the lower surrounding edge portion 33 and has
a retaining protrusion 327 formed thereon. When the upper surrounding
edge portion 321 is forced to extend outwardly of the upper open
end 212 of the barrel 20 after the tubular needle seat 30 is inserted
into the passage 21 the lower segment 322 will be brought to a
position of use, as shown in FIG. 4 where the lower segment 322
engages and is retained at the smaller-diameter segment 214 by virtue
of a first friction force generated as a result of retaining engagement
of the retaining protrusion 327 in the retaining groove 223 while
an upper edge surface 331 of the lower surrounding edge portion
33 abuts against the first surrounding shoulder portion 215 of the
barrel 20. The lower segment 322 further has an axially extending
friction spline portion 328 which cooperates with the friction spline
portion 216 of the smaller-diameter segment 214 to form a spline
member so as to prevent relative rotation between the needle seat
30 and the barrel 20. The upper segment 323 is disposed opposite
to the lower segment 322 and proximate to the upper surrounding
edge portion 321 and is adapted to be sleeved over by the needle
hub 42 of the needle unit 40 so as to communicate the duct 31 of
the needle seat 30 with the needle hub 42.
The plunger 50 includes a stem portion which is movable in the
passage 21 of the barrel 20. The stem portion has a plurality of
wing plates 53 angularly displaced from one another, a surrounding
flange 51 disposed on upper edges of the wing plates 53 a connecting
shank 54 extending from the surrounding flange 51 and a retaining
protrusion 542. The wing plates 53 are tapered downwardly. On the
other hand, the stem portion includes inner and outer segments 502501
opposite to each other in the longitudinal direction. The outer
segment 501 extends outwardly of the lower open end 211 of the barrel
20. An actuated end 52 which is a thumb rest, extends from the
outer segment 501 so as to be actuated to move the stem portion
along the passage 21.
The plunger 50 further includes a head which has a tapered surrounding
abutting portion 541 that extends from the retaining protrusion
542 of the inner segment 502 toward the grip segment of the needle
seat 30 and a spindle portion 55 which extends upwardly from the
surrounding abutting portion 541 along the axis and which terminates
at two split halves 552 553 that are spaced apart from each other
in a direction transverse to the longitudinal direction with a concave
space 551 in between. The split halves 552 553 respectively have
upper terminal anchoring edges 554 555. Preferably, the spindle
portion 55 has an outer diameter which decreases from the surrounding
abutting portion 541 toward the split halves 552 553.
A deformable surrounding engaging portion 60 such as made of an
elastic material, is retainingly sleeved on the whole retaining
protrusion 542 of the inner segment 502 and a portion of the surrounding
abutting portion 541 to generate a second friction force. The surrounding
engaging portion 60 has upper and lower end faces 64 65 opposite
to each other in the longitudinal direction and proximate to and
distal from the lower surrounding edge portion 33 of the needle
seat 30 respectively, and an outer surrounding surface 63 disposed
therebetween. The lower end face 65 is distal from the surrounding
flange 51 by a space (S). The outer surrounding surface 63 sealingly
contacts and is slidable relative to the larger-diameter segment
213 of the barrel 20 so as to be moved with the stem portion. Preferably,
the outer surrounding surface 63 is concaved toward the axis X to
decrease contact area between the outer surrounding surface 63 and
the larger-diameter segment 213 so as to facilitate sliding movement
of the surrounding engaging portion 60 relative to the larger-diameter
segment 213.
With reference to FIG. 5 in use, the plunger 50 is pressed forwardly
to push the upper end face 64 of the surrounding engaging portion
60 to abut against a lower edge surface 332 of the lower surrounding
edge portion 33 of the needle seat 30. Since the spindle portion
55 is configured to be tapered upwardly and to match with the inner
tubular wall surface 324 of the needle seat 30 drug solution in
the passage 21 can almost be completely injected via the needle
unit 40.
Subsequently, referring to FIG. 6 when the plunger 50 is further
moved forward by a third force towards the smaller-diameter segment
214 against the second friction force between the inner segment
502 and the surrounding engaging portion 60 the surrounding engaging
portion 60 is deformed by the lower surrounding edge portion 33
thereby decreasing the space (S) and permitting the surrounding
abutting portion 541 of the head to move in the concave portion
326 of the needle seat 30 to abut against the second surrounding
shoulder portion 329.
Meanwhile, the split halves 552 553 of the spindle portion 55
are pressed by the inner tubular wall surface 324 to move towards
each other against a biasing action when the split halves 552 553
are moved towards the upper surrounding edge portion 321. Once the
split halves 552 553 are moved beyond the upper surrounding edge
portion 321 the upper terminal anchoring edges 554 555 will engage
the upper surrounding edge portion 321 to generate a friction force
that combines with the friction force between the surrounding abutting
portion 541 and the second surrounding shoulder portion 329 to form
a fourth friction force that is greater than the first friction
force between the retaining protrusion 327 and the retaining groove
223.
After use, referring to FIG. 7 the outer segment 501 of the plunger
50 is pulled backward to be remote from the finger flange 23 so
that the needle seat 30 on which the used needle unit 40 is mounted,
is retracted into the passage 21 via the upper open end 212 to bring
the upper surrounding edge portion 321 to a retracted position.
When the surrounding flange 51 abuts against the protruding ring
217 further movement of the plunger 50 is prevented, thereby restraining
the surrounding engaging portion 60 from being removed out of the
lower open end 211. In this state, the used needle unit 40 can be
enclosed in the passage 21 of the barrel 20 for safe disposal.
Consequently, chances that the user may be accidentally pricked
or pierced by the needle are slim. The safety in use and disposal
is thus enhanced.
Furthermore, the wing plates 53 at the inner segment 502 have a
weakening area 531 disposed proximate to the surrounding flange
51. As such, when the plunger 50 is retracted to push the surrounding
flange 51 to abut against the protruding ring 217 the weakening
area 531 extends outwardly of the lower open end 211 so as to ease
breaking of the stem portion off the plunger 50 at the weakening
area 531 for convenient disposal.
Referring to FIG. 8 the second preferred embodiment of the disposable
syringe according to this invention is similar to the aforesaid
embodiment in construction. The differences therebetween reside
in that a retaining protrusion 742 and a surrounding abutting portion
741 of a plunger 70 are configured to be substantially hollow so
as to provide a greater flexibility, and that the spindle portion
in the aforesaid embodiment is dispensed with. An elastic surrounding
engaging portion 60 is retainingly sleeved on the whole retaining
protrusion 742 and a portion of the surrounding abutting portion
741. As such, when the surrounding engaging portion 60 is brought
by the stem portion 73 of the plunger 70 upwardly to engage and
is depressed by the lower surrounding edge portion 33 of the needle
seat 30 the surrounding engaging portion 60 is blocked by the lower
surrounding edge portion 33 thereby permitting the surrounding
abutting portion 741 to be retained in the concave portion 326
as shown in FIG. 9. Hence, the needle seat 30 and the needle unit
40 can be retracted into the passage 21 of the barrel 20 after an
injection procedure to permit breaking off the stem portion 73 of
the plunger 70 at a weakening area 731 for safe disposal, as shown
in FIG. 10.
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. |