TECHNICAL FIELD
5 [0001] The present invention relates generally to an outer needle assembly
including an outer needle and a passage forming member connected to the proximal
end side of the outer needle. More particularly, the present invention pertains to an
outer needle assembly including a ventilation path capable of discharging air from the
bore of the passage forming member to the outside, and a valve body by which the
10 bore of the passage forming member becomes in communication or blocked.
BACKGROUND ART
[0002] Conventionally, an outer needle assembly used for dialysis, infusion,
etc. has been known. For example, like an indwelling needle disclosed in Japanese
15 Unexamined Patent Publication No. JP-A-2015-080707 (Patent Document 1), the
outer needle assembly includes a hollow outer needle, and a passage forming member
such as an outer needle base connected to the proximal end side of the outer needle in
a communicating state. After the outer needle being stuck in a blood vessel of a
patient or the like together with an inner needle, the inner needle is removed, whereby
20 the outer needle assembly is indwelled in the blood vessel or the like. Then, dialysis
or infusion is performed by connecting an external passage such as a dialysis circuit
and an infusion line to an outer needle assembly indwelled in the blood vessel or the
like.
[0003] Besides, in the indwelling needle of Patent Document 1, a rubber
25 stopper part serving as a valve body is accommodated in the outer needle base, and by
opening and closing a slit valve provided in the rubber stopper part, communication
and blocking of the bore of the outer needle base can be switched. Specifically, in a
state where the inner needle is removed and the indwelling needle is indwelled in the
blood vessel, the slit valve of the rubber stopper part closes and the bore of the outer
30 needle base is blocked, so that blood leakage is limited. On the other hand, by
connecting the external passage to the outer needle base, the slit valve of the rubber
stopper opens so that the external passage communicates with the blood vessel via the
bore of the indwelling needle.
BACKGROUND ART DOCUMENT
35 PATENT DOCUMENT
[0004] Patent Document 1: JP-A-2015-080707
SUMMARY OF THE INVENTION
PROBLEM THE INVENTION ATTEMPTS TO SOLVE
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[0005] Meanwhile, in the outer needle assembly indwelled in the blood vessel,
before connection of the external passage, it is necessary to fill the bore with a liquid
such as blood and discharge air, so as to prevent the air from entering the blood vessel.
Therefore, in Patent Document 1, when the blood flows into the bore of the
5 indwelling needle (the outer needle assembly), the air will be discharged to the outside
through a gap serving as a ventilation path formed between the outer needle base and
the rubber stopper part.
[0006] However, research conducted by the inventors through tests has newly
revealed that when the outer needle assembly is tilted so that the needle tip points
10 diagonally upward and puncture is performed, in some instances, air is not sufficiently
discharged and remains in the bore of the outer needle assembly.
[0007] It is therefore one object of the present invention to provide an outer
needle assembly of novel structure which is able to prevent air from remaining.
MEANS FOR SOLVING THE PROBLEM
15 [0008] In order to prevent air from remaining in the bore of the outer needle
assembly, the inventors first tried to change the shape, size, number, arrangement, etc.
of the ventilation path. However, it was not possible to obtain a sufficient effect.
[0009] Next, the inventors observed in detail the flow mode of the liquid
(corresponding to blood) in the outer needle assembly by tests. As a result, it was
20 demonstrated that when the inner needle is pulled out from the outer needle from the
state of puncture of the inner needle shown in FIG. 7A to the state shown in FIG. 7B,
the liquid flowing from the needle tip of the outer needle was positioned so as to be
separated to the distal end side and the proximal end side in the outer needle assembly,
and discharge of air to the proximal end side was obstructed by the liquid, so that the
25 air remained between the liquid on the distal end side and the liquid on the proximal
end side.
[0010] The inventors examined the reason why the liquid introduced into the
bore of the outer needle assembly was separated to the distal end side and the
proximal end side with respect to the remaining air so that the air remained in the
30 middle of the liquid. During the examination, the inventors focused on the existence
of a stepped diameter-enlarged portion on the inner circumferential surface of the
outer needle assembly. It was presumed by the inventors that when such a stepped
diameter-enlarged portion was provided in the bore of the outer needle assembly, the
cross-sectional area of the bore of the outer needle assembly through which the liquid
35 flowed suddenly expanded on the way, whereby a region which was not filled with the
liquid would be generated at the diameter-enlarged portion. Then, it was considered
that the liquid reached the proximal end of the outer needle assembly while the air in
the region which was not filled with the liquid was remaining, and the ventilation path
was blocked by the liquid so as to obstruct discharge of the air through the ventilation
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path and the air remained in the middle portion of the outer needle assembly, whereby
the liquid existed on the opposite sides of the remaining air. Besides, according to
the review by the inventors, it was presumed that when the liquid flowed through the
stepped diameter-enlarged portion in the bore of the outer needle assembly, turbulence
5 was likely to occur due to a sudden change in the passage cross-sectional area,
whereby air entrainment in the liquid occurred and the discharge of the air became
insufficient, which was also one of the causes of the remaining air. Then, the
inventors have completed the present invention based on such findings.
[0011] Hereinafter, preferred embodiments for grasping the present invention
10 will be described. However, each preferred embodiment described below is
exemplary and can be appropriately combined with each other. Besides, a plurality
of elements described in each preferred embodiment can be recognized and adopted
as independently as possible, or can also be appropriately combined with any element
described in other preferred embodiments. By so doing, in the present invention,
15 various other preferred embodiments can be realized without being limited to those
described below.
[0012] A first preferred embodiment provides an outer needle assembly
comprising: an inner needle; an outer needle of hollow shape through which the inner
needle is inserted; a passage forming member connected to the outer needle; and a
20 valve body arranged inside the passage forming member, a first internal space on a
distal end side with respect to the valve body being longer than a second internal
space on a proximal end side with respect to the valve body, wherein a ventilation
path for discharging air in the first internal space to an outside communicates with the
first internal space in a vicinity of the valve body, and the first internal space
25 comprises: a puncture part formed in a portion of the outer needle, the portion
puncturing a blood vessel; a tapered part formed on the proximal end side with respect
to the puncture part, the tapered part having an inner diameter dimension which
increases toward the proximal end side; and a small-diameter part formed on the
proximal end side with respect to the tapered part, the small-diameter part having an
30 inner diameter dimension which is smaller than or equal to that of a proximal end of
the tapered part.
[0013] According to the outer needle assembly structured following the
present preferred embodiment, the cross-sectional area of the internal space at the
small-diameter part is equal to or smaller than the cross-sectional area of the internal
35 space at the proximal end of the tapered part. Thus, when the blood flows into the
small-diameter part via the puncture part and the tapered part, the blood is less likely
to wrap around the air to cause partial precedence, and the blood readily flows
through the entire cross section of the small-diameter part. As a result, it is unlikely
that the partially preceding blood passes the small-diameter part while leaving the air,
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and the blood blocks the ventilation path before the air is discharged. Accordingly,
the air in the small-diameter part will be pushed out to the ventilation path by the
blood without remaining and discharged to the outside. Therefore, even if the needle
tip is pointed diagonally upward and puncture is performed, the air is less likely to
5 remain in the first internal space on the distal end side with respect to the valve body.
[0014] The phenomenon of remaining air is likely to occur when the
ventilation path and the outer needle are largely separated from each other. Thus, the
configuration of the present preferred embodiment capable of preventing the air from
remaining is preferably applied to an outer needle assembly in which a ventilation
10 path and an outer needle are arranged at a large distance from each other by including
a tubular member between a member holding a valve body and a member holding the
outer needle or the like. Further, the configuration of the present preferred
embodiment is particularly preferably applied to an outer needle assembly in which
the length of the small-diameter part is longer than the distance from the distal end of
15 the tapered part to the distal end of the small-diameter part. Additionally, a
large-diameter part having an inner diameter larger than the small-diameter part is
formed on the proximal end side with respect to the small-diameter part, and the
large-diameter part may be adjacent to the valve body.
[0015] A second preferred embodiment provides an outer needle assembly
20 comprising: an inner needle; an outer needle of hollow shape through which the inner
needle is inserted; a passage forming member connected to the outer needle; a valve
body arranged inside the passage forming member; and a ventilation path provided to
the passage forming member and placing an internal space on a distal end side with
respect to the valve body in communication with an outside, wherein a proximal end
25 portion of the outer needle has a tapered shape that is enlarged in diameter toward a
proximal end, in a connecting portion between the outer needle and the passage
forming member, an inner diameter dimension of the passage forming member is
equal to or smaller than that of the outer needle.
[0016] According to the outer needle assembly structured following the
30 present preferred embodiment, the diameter-enlarged portion whose proximal end side
is increased in diameter is not formed at the connecting portion between the outer
needle and the passage forming member. Therefore, at the connecting portion
between the outer needle and the passage forming member in the bore of the outer
needle assembly, a region which is not filled with the liquid introduced from the outer
35 needle into the passage forming member is less prone to be formed, thereby suppress
remaining of the air.
[0017] Besides, since the proximal end portion of the outer needle has a
tapered shape whose diameter is enlarged toward the proximal end, the flow velocity
of the liquid flowing through the outer needle decreases toward the proximal end.
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As a result, occurrence of turbulence due to the flow of the liquid is further
suppressed at the proximal end of the outer needle, thereby preventing the air
entrainment in the liquid.
[0018] A third preferred embodiment provides the outer needle assembly
5 according to the second preferred embodiment, wherein in the connecting portion
between the outer needle and the passage forming member, the inner diameter
dimension of the passage forming member is equal to that of the outer needle.
[0019] According to the outer needle assembly structured following the
present preferred embodiment, the formation of a step is prevented at the connecting
10 portion between the outer needle and the passage forming member. Thus,
occurrence of turbulence is further reduced in the liquid flowing through the bore of
the outer needle assembly, thereby suppressing the air entrainment.
[0020] A fourth preferred embodiment provides the outer needle assembly
according to any one of the first through third preferred embodiments, wherein the
15 passage forming member includes a flexible tube, and the flexible tube is connected to
the outer needle.

CLAIMS
1. An outer needle assembly comprising:
an inner needle;
5 an outer needle of hollow shape through which the inner needle is inserted;
a passage forming member connected to the outer needle; and
a valve body arranged inside the passage forming member, a first internal
space on a distal end side with respect to the valve body being longer than a second
internal space on a proximal end side with respect to the valve body, wherein
10 a ventilation path for discharging air in the first internal space to an outside
communicates with the first internal space in a vicinity of the valve body, and
the first internal space comprises:
a puncture part formed in a portion of the outer needle, the portion
puncturing a blood vessel;
15 a tapered part formed on the proximal end side with respect to the
puncture part, the tapered part having an inner diameter dimension which increases
toward the proximal end side; and
a small-diameter part formed on the proximal end side with respect to
the tapered part, the small-diameter part having an inner diameter dimension which is
20 smaller than or equal to that of a proximal end of the tapered part.
2. An outer needle assembly comprising:
an inner needle;
an outer needle of hollow shape through which the inner needle is inserted;
25 a passage forming member connected to the outer needle;
a valve body arranged inside the passage forming member; and
a ventilation path provided to the passage forming member and placing an
internal space on a distal end side with respect to the valve body in communication
with an outside, wherein
30 a proximal end portion of the outer needle has a tapered shape that is enlarged
in diameter toward a proximal end,
in a connecting portion between the outer needle and the passage forming
member, an inner diameter dimension of the passage forming member is equal to or
smaller than that of the outer needle.
35
3. The outer needle assembly according to claim 2, wherein in the connecting
portion between the outer needle and the passage forming member, the inner diameter
dimension of the passage forming member is equal to that of the outer needle.
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4. The outer needle assembly according to any one of claims 1-3, wherein the
passage forming member includes a flexible tube, and the flexible tube is connected to
the outer needle.
5 5. The outer needle assembly according to claim 4, wherein a distal end portion
of the flexible tube includes a large-diameter tube part whose inner diameter
dimension is increased, and a proximal end portion of the outer needle is fastened to
the large-diameter tube part in an inserted state.
10 6. The outer needle assembly according to claim 5, wherein the flexible tube
includes a small-diameter tube part provided on the proximal end side with respect to
the large-diameter tube part, the small-diameter tube part having an inner diameter
dimension and an outer diameter dimension that are smaller than those of the
large-diameter tube part.
15
7. The outer needle assembly according to any one of claims 1-6, wherein the
passage forming member includes a flexible tube, and an inner circumferential surface
ranging from a distal end of the outer needle to a proximal end of the flexible tube is
not provided with a stepped diameter-enlarged portion.
20
8. A needle assembly comprising:
a needle;
a passage forming member connected to the needle; and
a valve body arranged inside the passage forming member, a first internal
25 space on a distal end side with respect to the valve body being longer than a second
internal space on a proximal end side with respect to the valve body, wherein
a ventilation path for discharging air in the first internal space to an outside
communicates with the first internal space in a vicinity of the valve body, and
the first internal space comprises:
30 a puncture part formed in a portion of the needle, the portion
puncturing a blood vessel;
a tapered part formed on the proximal end side with respect to the
puncture part, the tapered part having an inner diameter dimension which increases
toward the proximal end side; and
35 a small-diameter part formed on the proximal end side with respect to
the tapered part, the small-diameter part having an inner diameter dimension which is
smaller than or equal to that of a proximal end of the tapered part.