Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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EASY USE NEEDLE PROTECTOR SHEATH
TECHNICAL FIELD
Many types of needle protector sheaths are known.
Particularly, needle protector sheaths for winged
~ needles are presently in clinical use, in which the
wings of the needle project outwardly through slits
defined in the sheath, so that the sheath can slide from
a retracted position while the needle is in use to an
advanced positioned in which the needle is enclosed, the
sheath being locked in that position so that the point
of the needle is recessed in the sheath and cannot cause
accidental injury. For examples of such devices, see
Utterberg et al. U.S. Patent No. 5,112,311; Shields U.S.
Patent No. 5,350,368; Gollobin et al. U.S. Patent No.
5,330,438; Masters et al. U.S. Patent No. 4,941,881;
Japanese Patent Publication 1-212,561; and Fayngold U.S.
Patent No. 5,120,320 among others.
As one disadvantage of such protector sheaths for
needles, since they carry a slit it is at least remotely
possible for the needle to rotate in a horizontal manner
after it has been placed in the sheath, causing the
needle tip to project laterally out of one of the slits,
where it may cause accidental in~ury.
As another issue, the clinicians who use the
needle protector sheaths wish to make sure that the
wings of the needles are securely latched into a rear
end portion of the slots as the sheath is advanced, so
that the sheath will not accidentally retract, again
exposing the needle. With earlier designs, some
difficulties have been encountered in easily moving the
needle and wings into a retracted, latched position
where the needle tip is securely recessed, while at the
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same time assuring that the point of the needle is
securely retained within the sheath in a position where
it cannot shift and project laterally outwardly through
one of the slots.
By this invention, improvements are provided to
medical needle protector sheaths to give greater
assurance that the sheath and needle are locked together
after needle use, with the needle being reliably
positioned in retracted position within the sheath, so
that any possible accidental failure resulting in the
needle projecting out of the sheath again is eliminated.
Particularly, one can easily move the needle and
wings into a retracted, latched position where the
needle tip is securely recessed, while at the same time
assuring that the point of the needle is securely
retained within the sheath in a position where it cannot
shift and project laterally outwardly through one of the
slots.
Furthermore, in the use of fistula needles for
hemodialysis and the like, some nurses insert the needle
into a patient with the bevelled tip of the needle end
facing up, and some insert the needle with the bevelled
tip down. In many of the prior art needle guards, this
can significantly affect the utility of the guard in
catching and holding the needle as it is withdrawn from
the patient in the customary manner. Most current
fistula needle wings project from their hub from a
position that is laterally spaced from the center line
defining the needle axis. Thus, with many of the prior
art slotted needle guards, if a needle has been inserted
into a patient with a bevelled needle point up, the wing
may pass through the slots of the guard with most of the
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needle and hub being positioned above the slots (when
~iewed from the side). However, if the same needle is
inserted into a patient with the bevelled needle tip
down, then the needle and hub will be positioned mostly
below the slot. ln each case, of course, the wings will
occupy the slot, but the positioning of the rest of the
needle and the hub may be substantially changed.
Thus, many of the slotted needle guards of the
prior art work poorly for needles and hubs that have
been inserted into the patient in an "upside down"
manner, from the viewpoint of the design of the prior
art slotted guard.
If many of the prior art needle guard sheath
configurations were made of a deformable plastic so as
to be forgiving as to differences in the dimensions of
winged needles, (and particularly the difference in
dimensions between a winged needle and the same winged
needle in an inverted position) the same flexibility of
the sheath housing creates the risk that the prior art
catches used to hold the wings of the needle in a
retracted position in the sheath may accidentally
release the wings through flexing of the housing. Thus,
any prior art units that were deformable exhibited a
safety problem in that the needle and wings of the
winged needle could be accidentally released.
By this invention, a new type of catch is
provided, which is more forgiving to flexing of the
medical needle protector sheath of this invention, and
which more reliably holds the wings of needles, thus
preventing them from being accidentally removed from the
sheath or accidentally allowing the needle point to
project laterally outward through the slots.
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Furthermore, the prior art needle sheaths often
utilize an "anchor" as typically taught in Utterberg et
al. U.S. Patent No. 5,112,311. In the field of
dialysis, when a winged fistula needle is to be removed,
the nurse presses the site of needle entry with a wad of
gauze, while bringing the needle sheath up to a position
where one of her fingers can press on or otherwise grasp
the forwardly projecting "anchor". Then, the nurse
pulls the needle tubing, causing the needle to withdraw
and to retract back into locked relation with the
slotted sheath, while the sheath is prevented from
retraction by the manual pressure on the anchor. At
this moment, the nurse does not want to reduce finger
pressure on the gauze, which is preventing bleeding at
the needle access point. In the prior art, this r~~nc
that the nurse cannot conveniently release the anchor so
that the needle and set can be removed without a
reduction in finger pressure.
By this invention, the advantages of an anchor on
2~ the slotted sheath may be achieved, but at the same time
the sheath and needle may be removed without the nurse
letting up on the finger pressure on the gauze.
Furthermore, the protector sheath of this
invention holds the needle in a locked relation in which
the needle extends upwardly into substantial engagement
with the top wall of the sheath. This puts the tip of
the needle in vertically spaced relation to the slots in
the sidewalls, providing further assurance that the
needle tip cannot proiect out of a sidewall. This can
be facilitated by the use of an end wall which extends
downwardly part of the distance ~rom the top wall toward
a bottom wall of the sheath, forcing the needle hub and
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tubing downwardly, rather in a pivoting relation about
the wings in slot portions of the sheath, which, in
turn, forces and holds the needle tip up.
DESCRIPTION OF THE INVENTION
By this invention, a medical needle protector
sheath comprises a body having a top wall, side walls,
an open first end, and a slot formed in each side wall
to receive a needle wing extending through each of the
slots. The slots extend from the first end toward a
second end opposed to the first end, with the slots
terminating in the side walls at closed end points which
are spaced from the second end.
In one embodiment, first portions of the slots
are positioned adjacent to the end points, the first
slot portions sloping away from the top wall as the
slots extend toward the second end.
The protector sheath further preferably comprises
a bottom wall which is connected to the side walls. The
bottom wall may be spaced inwardly from the second end
of the sheath to define a recess. This can permit a
needle and hub positioned in the sheath, particularly
with the needle wings positioned in the first, sloping
slot portions, to be tilted so that the needle tip
preferably engages and can dig into the top wall. As
this takes place, the hub may occupy at least some of
the recess defined by the inward spacing of the bottom
wall.
It is also preferred for an end wall to be
defined at the second end of the sheath. This end wall
extends from the vicinity of the top wall, and is
preferably integral therewith. The end wall may define
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a smooth, downwardly extending curve from the top wall,
or may be of another shape, extending downwardly to a
position above the bottom wall to provide room for the
needle hub and connected tubing to extend out of the
second end of the sheath. The end wall firmly holds and
constrains the needle and hub in a desired acute angle
to the top wall, which acute angle may correspond to a
lesser or equal angle of the first portions of the
slots. Typically, the needle hub or its tubing may abut
the lower edge of the end wall, which prevents it from
being raised or rotated about its wings to put the
needle and hub into a more parallel relation with the
protector sheath. At the same time, the needle and hub
may constrained against rotation in the other direction
by the impinging of the needle or its tip against the
top wall of the sheath. Thus, the needle and hub may
not only be retained in firm, non-moving relation to the
sheath by conventional first catch projections defined
in the first portions of the slots, but it can be held
against rotation relative to the sheath by the points of
impingement at the bottom of the end wall and between
the needle point and the top wall.
It is also preferred for the slots to define
second portions, which are positioned adjacent to the
first slot portions but nearer to the first end than the
first slot portions. These optional second slot
portions define a greater slot width than other slot
portions, to permit a degree of free vertical rotation
of the wings of a medical needle which occupy the second
slot portion. Thus, while the needle occupies the
second slot portion, it can rotate with ease through a
certain, constrained angle. This is particularly
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advantageous when, as is preferred, most of the parts o~
the slots positioned between the first slot portion and
the first sheath end slope toward the top wall as the
slots extend towards the second end. Such a slot shape
without the second portions is taught in the Utterberg
U.S. Patent Nos. 5,562,636 and 5,562,637.
Since the respective slots first extend upwardly
toward the top wall, and then curve downwardly again
away from the top wall, the needle and hub must rotate
as their wings slide along the slots, when the needle is
being retracted into the sheath. The second portions of
the slots, permitting a degree of free rotation of the
needle, facilitate the retraction process, reducing the
force necessary to bring the sheath and needle together
into latched relationship.
It is also preferred for an upstanding handle for
manual retention of the sheath to project from the top
wall at or near the first end of the sheath. This
provides a better grip on the sheath than has been
previously provided, so that the needle may be pulled
~rom its position within the patient by pulling the
connected tube, causing the needle to retract to slide
along the slots, and to latch into position with a
discernable snap. rhis indicates reliable latching of
the sheath in protective position around the needle.
While one finger hoids the upstanding handle, other
fingers of the user may press overlying gauze (as
generally described in the previously cited Utterberg
U.S. Patent No. 5,112,311) to suppress bleeding after
needle removal in conventional manner.
If desired, the upstanding handle may be a finger
ring. The handle may be defined on a ~orward extension
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of the top ~all which extends forwardly beyond the side
walls at the first end.
It also may be desirable for the top wall of the
sheath to define an elevated portion adjacent to the
first end, which correspondingly provides an elevated
space inside the sheath. This permits use of the sheath
with longer needles, providing a broader range of needle
lengths with which a single protector sheath may be
used.
In another embodiment, the sidewalls define at
least one catch projection which is spaced from the
closed ends of the slots, to prevent needle wings that
occupy the first slot portions from easily sliding away
from the first slot portions. The catch projection
defines an elongated member having a first end that
defines a wing catching tip extending into one of the
slots. The elongated member is attached to the sidewall
only at an elongated member end that is opposed to the
first end, to permit the elongated member to flex in the
sidewall plane. Also, the elongated member preferably
extends into a direction that defines an acute angle to
at least the majority of the top wall, with the first
end facing the first slot portion.
Preferably, the wing catching tip of the
elongated member is either in contact with the upper
surface of the slot or in close proximity thereto.
Particularly, it is preferred for the elongated member
to be spaced, in its normal, unflexed position, from the
slot upper edge by a distance which is less than the
thickness of the needle wings that the sheath is
designed to retain.
Preferably, the first slo~ portions extend at an
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acute angle away from the top wall from the vicinity of
the elongated members to the closed slot ends.
As before, the sheath may further comprise a
bottom wall, and an end wall at the one body end which
is adjacent to the slot closed end portions. The end
wall extends from the vicinity of the top wall
downwardly to a position above the bottom wall, if
present or otherwise above the bottoms of the sidewalls,
so that, as a result of this, the needle and hub may be
held in the sheath at an acute angle to the top wall
when the wings occupy the first slot portions.
Also, portions of the slots which are more
remotely spaced from the end wall than the elongated
member may extend from the vicinity of the elongated
member in an acute angle away from the top wall to open
slot ends at the needle protector sheath end which is
opposed to the one end.
The sheath may also have a flexible, upstanding
handle which is preferably of C-shape, for manual
retention of the sheath. This handle may project from
the top wall adjacent the end of the sheath which is
opposed to the one end. Also, the handle may
communicate with the top wall of the sheath through a
line of flexing weakness, to facilitate the flexibility
of the handle. Thus the user, while withdrawing a
winged needle into the sheath, may hold the upstanding
handle with a finger. The handle may have sufficient
stiffness to permit the needle to be pulled into the
sheath and locked therein, but the handle is
sufficiently flexible so that the sheath may be removed
from the finger that the handle engages by flexing
without a need to move the finger.
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The sheath may also be made of a flexible plastic
so that it can receive and hold winged needles of a
variety of shape configurations, which includes, as
previously discussed, needles which are of differing
dimension relative to the plane of the wings, when
inverted. Also, the elongated member may carry a
longitudinal strengthening rib.
By the use of the above features either together
in various combinations or separately, significant
advantages may be achieved in the use and handling of
winged needle protector sheaths.
DESCRIPTION OF THE DRAWINGS
In the drawings, Fig. 1 is an elevational view of
a first embodiment of the needle sheath of this
invention;
Fig. 2 is an elevational view of a second
embodiment of the needle sheath of this invention,
showing a needle carried therein;
Fig. 3 is an end elevational view of the needle
sheath of Fig. 1 and Fig. 2;
Fig. 4 is a bottom plan view of the needle sheath
of Fig. 1 and Fig. 2;
Fig. 5 is a side elevational view of a third
embodiment of the needle sheath of this invention;
Fig. 6 is a side elevational view of a fourth
embodiment of the needle sheath of this invention;
Fig. 7 is a perspective view of a needle sheath
of this invention, carried on a fistula set for
hemodialysis;
Fig. 8 is an enlarged elevational view of the
first or back end of the sheath, showing how a wing of
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the needle, shown in section, can move to the first slot
portion adjacent the one end of=the body; and
Fig. 9 is an enlarged elevational view of the
complete protector sheath, showing how the wing of the
needle is held in position within the first slot portion
by the catch projection;
DESCRIPTION OF SPECIFIC EMBODIMENTS
Referring to the drawings, Fig. 1-6, shows a
hollow needle sheath 10 which has a top wall 12, side
walls 14, 16, and a bottom wall 18, being positioned in
rectangular array in a manner similar to that shown in
Fig. 3. Needle sheath 10 also defines an inner bore or
lumen 20 of generally rectangular shape, being at least
partially open at each end.
Sheath 10 also defines slots 22 extending through
first end 24 of the sheath and extending toward second
end 26. Each of slots 22 are of substantially identical
shape and terminate at respective end points 28 at a
position spaced from second end 26.
As shown in Fig. 2, sheath 10 may be threaded on
a winged needle which is connected to a tube in
conventional manner. The needle may be originally
positioned in the venous system of a patient. Thus,
when the needle is withdrawn, it slides to the rear,
with the wings entering slots 22 or 22a. Initially the
needle is angled slightly upwardly as it occupies the
skin of the patient, similar to that shown in Fig. 14 of
Utterberg Patent No. 5,112,311, at an angle
approximately parallel to the forward section 30 of slot
22 as it rests on the skin of the patient. Thus, as the
needle is pulled backwards out of the patient, it slides
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diagonally upwardly along forward slot sections 30, 3Oa
in a manner that m; n;~;zes twisting and bending of the
needle while the needle tip remains in the patient.
Then, the wings of the needle enter a second slot
section 32, 32a as defined above, which is of increased
width relative to other portions of the slots 22.
Because of this increased width, the needle wings are
free to rotate out of connection, for example, with the
lower edge 34 of slot section 32 into engagement with
upper edge 36 of second slot section 32, causing the
needle to rotate in clockwise manner into a position
similar to that shown in Fig. 2. Fig. 2 shows a needle
sheath similar in its basic construction to that of Fig.
1 except for the construction of upstanding handle 44,
44a, carried on a forward extension 3g, 38 of upper wall
12, 12a.
The needle i5 pulled backwards into snap-fit
relation with a first section 40, 4Oa of the slots,
which section carries a generally conventional catch
projection 42, 42a for retention of the wings in the
respective first slot sections 40, 40a. The presence of
the widened second slot section 32, 32a permits the
spontaneous rotation and the easy transition of the
needle and wings to a different angle as the needle is
drawn backwards into sheath 10 and into locking relation
therewith in first slot section 40. Thus, the necessary
pulling force to accomplish this is reduced.
Upstanding handle 44 of Fig. 1 simply represents
an upwardly turned projection which may be retained by
the finger of the user's hand. Typically with the same
hand, the user is covering the needle injection site of
the patient with gauze pads. Thus, one can remove the
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needle from the patient by pulling the hub or its
connected tubing 58, causing the needle to retract into
the sheath. As this is done, one can firmly hold handle
44, 44a of the sheath with one finger to prevent it from
retreating with the needle.
In Fig. 2, the upstanding handle 44a may be a
hollow tube or a ring, preferably of approximately the
width of sheath lOa as shown in Fig. 4. The various
reference numerals of Figs. 2 and 4 which end with
suffix "a" correspond to the parts referred above by the
corresponding numbers of Figs. 1 and 3 without the
suffix. For example, bottom wall 18a of Figs. 2 and 4
correspond to bottom wall 18 of the Fig. 1 embodiment.
Both of the embodiments of Figs. 1 and 2 define
a bottom wall 18, 18a which are connected to the side
walls, but are spaced inwardly from the second end 26,
26a to form an optional recess 46, 46a. Coupled with
this, it is preferred for an end wall 48, 48a to connect
with the top wall 12, 12a and to curve downwardly from
the top wall to a bottom position 49 above bottom wall
18, 18a that permits winged needle and hub assembly 50
to extend into the bore 20 underneath end walls 48, 48a.
Typically, as shown in Fig. 2, the wings 52 of assembly
50 are held in an angle to the longitudinal axis of
sheath 10, lOa as they occupy first portion 40, 40a of
the slots, which first portion occupies a similar angle.
The presence of end wall 48 prevents assembly 50 from
rotating upwardly by flexing wings 52, because such
countercloc~wise rotational motion is prevented by the
abutment of assembly 50 against the lower edge of end
wall 48 or 48a. However, needle and hub 50 does not
have to abut end wall 48. It may ke spaced from it.
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Also, in the ~ully retracted, locked
configuration of needle assembly 50 as shown in Fig. 2,
the upwardly angled needle point 56 preferably presses
against top wall 12a, being directed there by the angle
and position of slot portions 40a and the position of
the lower edge o~ end wall 48a. Thus, needle tip 56
presses against top wall 12, 12a when in its fully
retracted and locked position, with the wings being
locked in generally conventional manner in first slot
portion 40a. This also prevents needle assembly 50 from
rotating in clockwise manner around the flexible wings,
so that the needle assembly is rigidly affixed within
sheath lOa, being incapable of rotation about the
flexible wings 52 because of the engagement at the lower
edge of end wall 54 and at the point of engagement of
needle tip 56 against the undersurface of top wall 12a.
The aperture 46a in the bottom wall makes is
possible for needle assembly 50 to project slightly
below the side walls as necessary to achieve this
configuration. Also, if desired, the wall that defines
aperture 46a may serve as a secondary catch for the
annular face of the tubing 58 to which the needle is
attached.
Similar relationships may be applied between a
winged needle hub and the Fig. 1 embodiment.
Referring to Fig. 5, another embodiment of the
sheath of this invention is disclosed. Sheath lOb can
be of identical structure to that of the previous
designs except as otherwise described herein. The
difference lies near the first end of sheath lOb, while
slot 22b and most of the length of the respective walls
can be identical to the above.
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It can be seen that on the left side of the
sheath of Fig. 5, the extension of top wall 38, 39 has
been eliminated, and a different, upstanding handle 60
is provided in the form of a finger ring which attaches
to top wall 12b at two different places 62, 64. Also,
top wall 12b defines an externally and internally
elevated portion 66, which allows longer needles 56a or
shorter needles to be retained in the same guard, with
their respective wings 52a sliding along the slot 22b
into first slot portion 40b with substantially the same
catchment angle as shorter needles. Upstanding finger
ring 60 provides good ergonomic characteristics, which
isolate the needle withdrawal traction forces that may
be resisted by the finger in ring 60 from the needed
pressure on the overlying gauze by other fingers, as the
needle is being withdrawn from the patient, to provide
hemostasis.
Apart from that, sheath lOb can be of identical
design, and can work in a manner identical to, the
sheaths of the previous embodiments. Note that the
needle 56a may be placed into the sheath 18a with a
point inverted from the position of needle point 56.
Either position is suitable for these sheaths.
Referring to Fig. 6, another embodiment of sheath
lOc may be of similar structure and function to the
previous sheaths except as otherwise described herein.
The end wall 48c at the second end of sheath lOc partly
but not completely blocks the bore extending through the
hollow sheath lOc, to serve as a structure equivalent to
end walls 48, 48a for similar purposes of holding the
rotational orientation of a needle and hub 50 captured
within the sheath. As one difference, end wall 48c may
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be an angled straight wall, rather than a curved wall as
in the previous embodiments, extending down to bottom
position 54c.
At the other end of the sheath lOc, the
upstanding handle for manual retention 60c comprises a
partial arc attached to the rest of sheath lOc at only
one end, as shown. This structure is also suitable for
being gripped with one finger to hold sheath lOc in its
desired position as the needle is being pulled out of
the patient and into retracted relation within the
sheath lOc.
Upstanding handle members 60, 60c have widths
preferably substantially identical to the widths of
sheaths lOb, lOc in a manner similar to that generally
indicated in Fig. 3, although other widths may be used
if desired.
Thus, a sheath for winged medical needles is
provided, in which the needle may be comfortably and
reliably pulled from the patient while the sheath is
manually retained with a finger, and the wings slip into
the respective slots 22, to encourage the needle to
withdraw from the patients' skin at a shallow angle
which approximates the axis of the needle in the skin.
This reduces pain. Then, as the needle wings are being
withdrawn through slots 22 and enter into the second
slot section 32, the needle can spontaneously rotate
through a small angle so that the wings become more
parallel to the direction of first slot section 40 which
extends at a different angle. The needle is thus
rotated upwardly so that its tip can press against the
lower surface of the upper wall 12, being held there so
that the needle cannot accidentally pass through one of
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the slots to the exterior.
~ eferring to Figs. 7-9 drawings, medical needle
protector sheath 100 is shown to be carried on tubing
120 of a conventional winged needle fistula set 140,
having a needle 16, closed with a removable needle guard
180,, and having wings 200 projecting outwardly from hub
170. The tubing 120 can be seen to be extending
entirely through the hollow interior of protector sheath
100 .
Protector sheath 100 comprises a body having a
top wall 220, sidewalls 240, and a slot 260 formed in
each sidewall to receive a needle wing 200 as the needle
is retracted from the patient rearwardly into protector
sheath 100 and held there by latching of the wings.
The respective slots 260 define first slot
portions 280, each o~ the first slot portions having one
closed end 290 adjacent one end 300 of the body of
sheath 100.
The respective sidewalls 240 each define a catch
projection 320, each of which is spaced from the
respective closed end Z90 o~ slot portion 280, and which
serves to prevent needle wings that occupy first slot
portions 280 from easily sliding away from the first
slot portions. Catch projections 3Z0 are also
sufficiently flexible, as particularly shown in Fig. 8,
to be deflected downwardly as the respective needle
wings 200 slide from the open mouth 340 of slots 260,
along the slots, to enter the first slot portions 280 by
deflection of catch projections 320 as in Fig. 8. Then,
as shown in Fig. 9, catch projections 320 can spring
back into their original configuration in which a wing
catching tip 330 of the catch projection 320 is either
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in contact with the upper surface 360 of slot 280 or in
close proximity thereto, less than the thickness of the
wings 200. Thus, as Fig. 9 illustrates, the respective
wings 200 are not easily removed from their occupancy of
the first slot portions 280 once they have entered the
first slot portions. Thus, the sharp point of needle
160 is also retained within the protector sheath,
typically being pressed against the underside of top
wall 220 because the first slot portions 280 extend at
an acute angle away from top wall 220 from the vicinity
of elongated members 320 to the closed ends 290, as
shown in phantom lines 160 in Fig. 9. Typically this
acute angle is about 5 to 20 degrees. Also, end wall
400 presses tube 120 to help hold needle 160 upto engage
the top wall 220.
Elongated member 320 may carry a longitudinal
strengthening rib 330.
Sheath 100 also comprises a bottom wall 380 and
an end wall 400 at and adjacent the one body end 300.
End wall 400 extends from the vicinity of top wall 220
downwardly in an angled manner to a position above
bottom wall 380, so that an aperture 420 is provided in
a lower portion of the sheath, through which tubing 120
can extend. However, as shown particularly in Fig. 7,
tubing 12 is thus forced downwardly by endwall 400, away
from top wall 220, which, in turn, facilitates the
forcing of the needle 160 to upwardly rotate at flexible
wings 200, to assure an upward position of needle 160 as
shown in Fig. 9 so that the sharp point is well out of
harm's way, and also to prevent the sharp needle point
from accidentally projecting outwardly through one of
slots 260.
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The remaining portions 440 of slots 260, which
are more remotely spaced from end wall 290 than
elongated member 320, may extend from the vicinity of
elongated member 320 in an acute angle away from top
5 wall 220 to the open slot ends 340. Typically, this
acute angle is also about 5 to 20 degrees, as is the
corresponding acute angle of first slot portion 280.
At the end of the sheath which is opposed to
first end 300, an integral, flexible, upstanding handle
460 may be carried, for manual retention of the sheath.
The flexibility of handle 460 may be enhanced by the
presence of a transverse line of flexing weakness 480.
The medical needle protector sheath of this
invention may comprise a single, integrally molded piece
made of a plastic which is somewhat flexible at the
dimensions used. Thus, as previously described, the
sheath can be used with winged needles in which the
wings 20 are spaced from the longitudinal axis of the
set as defined by the axis of needle 16 irrespective of
whether the needle and set are in use with the bevelled
tip 50 facing downwardly as shown in Fig. 7 or in an
inverted position where the bevelled tip 50 faces
upwardly. The flexibility of sheath 100 can accommodate
the differing dimensions or location of the wings in
these two circumstances because of the design of the
elongated member 320 of the catch projection, as shown.
The front surface 520 of elongated member 320 is angled
slightly forwardly from bottom to top so that when wing
200 is attempted to be retracted along the slots toward
30 their mouths 340, the elongated member 320 of the catch
projection is forced upwardly by the wing to engage the
upper wall 360 of slot portion 280. Thus, no amount of
CA 022l4989 l997-09-09
W097/2~82 PCT~S96/20740
pulling, apart from destruction, can cause wings 200 to
be dislodged out of their locked position, and this
situation continues to hold even when the sheath is
twisted, opened, or otherwise manually deformed.
Accordingly, as taught in Utterberg U.S. Patent
No. 5,112,311, the fistula needle 160 iS positioned in
the vein of a patient, and the wings are strapped to the
skin. For removal of the fistula needle, the wings are
released from their adhesive tape straps; a wad of gauze
is placed on the puncture site of the needle to the
skin; and the nurse presses the gauze on that point
while hooking one finger around upstanding handle 460.
Then, the nurse simply pulls on tubing 120 to withdraw
needle 160, causing the needle and wings to retract back
into protector sheath 100, with the wings 200 sliding
through slots 260. The acute angle of slot 260 is
present to match the approximate angle of needle 16 to
the skin of the patient, so that the needle is not
twisted as it is withdrawn. Then, as the needle
20 continues to be withdrawn, sliding through slots 260,
the wings 200 depress elongated member 320 of the catch
projection, permitting the wings to slide into first
slot portions 280. When the wings arrive in first slot
portions 280, catch projections 320 spring back to their
original position, as shown in Fig. 9, firmly and
reliably retaining wings 200 in the position of
occupying first slot portion 280. Simultaneously, since
first slot portion 280 occupies an acute angle of
opposite sense to the acute angle of the rest of slot
260, and also because of the presence of wall 400 that
forces tube 120 downwardly, needle 160 is forced to
rotate upwardly so that the tip impacts against the
CA 02214989 1997-09-09
'W097/25082 PCT~S96/20740
lower surface of wall 220, where it is firmly held out
of harm's way.
The above has been offered for illustrative
purposes only, and is not to be construed as limiting
the scope of the invention of this application, which is
as defined in the claims below.
