Note: Descriptions are shown in the official language in which they were submitted.
CA 02044818 2003-O1-23
DISCLOSURE OF INVENTION
TITLE: Needle-Mounted Needle Guard for Intravenous
Catheters
1. FIELD OF THE INVENTION
1.1. This invention relates to the safe disposal of
hypodermic needles by a guard device which protects the
needle tip from exposure after use. More particularly, it
relates to a mechanism for a tip protector which is storable
on the needle and which automatically locks over the end of
.LO the needle when slid into position at the needle tip by the
user. It relates specifically to a needle guard mounted on
and positively engaged with an intravenous catheter and
which disengages from the catheter automatically when the
needle guard locks over the end of the catheter insertion
.L5 needle.
2. BACKGROUND TO THE INVENTION
2.1 The type of needle guard to which this invention
relates has been described in Patent Cooperation Treaty
application No. PCT/CA90/00031 published on Aug. 9, 1990
:?0 under international publication number WO 90/08564.
2.2 Improvements to this prior PCT application are
further described in Canada Patent application No. 2,033,361
filed on December 28, 1990.
2.3 These cited prior applications describe a range of
:?5 configurations for needle guard devices which are stored at
the base of a needle and which automatically engage with and
cover the tip of a needle when moved to the tip.
2.4 One embodiment in the cited prior Canadian patent
application relates to the installation of the needle guard on
:30 an intravenous catheter assembly, in which the needle guard is
1
frictionally retained on the base or hub of the catheter, until
the needle guard locks over the tip of the insertion needle, as
the latter is withdrawn from the catheter. Continued needle
withdrawal motion is then transmitted to the locked needle guard,
and additional withdrawal force overcomes the frictional grip of
the needle guard on the catheter hub, allowing the needle guard
to separate from the hub for disposal with the needle.
2.5 This embodiment requires that the user of the
intravenous assembly hold the catheter hub with hand A while
withdrawing the needle by pulling on its base with hand B. It
thus requires no change in the user's accustomed manipulative
procedure used with an ordinary catheter assembly.
2.6 However, if the user withdraws the needle by using hand
B to grip and pull the needle guard instead of the needle base,
the needle guard will separate prematurely from the catheter
while the needle point is still outside the body of the needle
guard, and therefore unprotected. This malfunction defeats the
purpose of the needle guard.
2.7 The above embodiment further requires that the
withdrawal force required to overcome the frictional grip on the
catheter hub of the locked needle guard be significantly greater
than the frictional drag between the needle and the needle guard
when the latter is being slid along the needle shaft during the
withdrawal motion. This is to ensure that the needle guard does
not separate from the catheter hub before the needle guard locks
over the needle tip. However, this frictional separation force
must not be excessive, as it may cause the catheter to be jerked
involuntarily toward and into the patient by the user's hand A at
the moment of separation, causing possible injury. These
conflicting frictional requirements place significant constraints
on the design of the needle guard assembly.
2.8 The invention described herein relates to a further
embodiment of the above prior applications whereby the needle
guard is retained on the catheter hub by a positive engagement
means between the needle guard and the hub, instead of by
friction. This engagement means is released only after the
needle guard has locked over the needle tip, allowing the needle
guard to separate from the catheter hub without significant
further withdrawal effort.
2.9 With this embodiment, if the user's hand B accidentally
grips the needle guard instead of the needle base during
withdrawal, the user will be unable to separate the needle guard
from the catheter hub, and must transfer the grip of hand B
correctly to the needle base before he can withdraw the needle.
2.10 Furthermore, if hand A should accidentally grip the
needle guard instead of the catheter in order to restrain the
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CA 02044818 2003-O1-23
catheter during withdrawal of the needle, the needle will draw out
and the needle guard will lock in the normal way. This will
release the needle guard to separate from the catheter hub with
little or no further pulling effort. It is therefore immaterial
whether the catheter is restrained with hand A by holding its hub,
or by holding the needle guard.
2.11 With this embodiment, the needle guard must lock to the
needle shaft, covering the needle tip, before the needle guard can
be released from its positive engagement with the catheter hub.
.LO Thus the needle tip cannot be exposed under any
circumstances, following attachment of the needle guard and needle
to the catheter hub.
3. SUMMARY OF THE INVENTION
3.1 According to this invention, a needle guard is provided
.L5 that may be installed at the base of a constant diameter insertion
needle of an intravenous catheter assembly and which remains
positively attached at the base of the catheter until the guard is
deployed at the needle tip.
3.2 The needle guard mechanism may be of the canted locking
:?0 plate type described in the cited prior applications comprising:
3.2.1 A body having an axial needle passageway
extending the length of the body, and also having
other laterally-accessible component cavities.
3.2.2 A canting lever with a locking plate at its one
:?5 end and a sensing plate at its other, installed
in one of the above component cavities.
3.2.3 A spring, mounted in one of the above component
cavities, and arranged to hold the sensing end
of
the lever in contact with the side of the
3 0 insertion needle shaft.
3.2.4 A shell of one or more pieces, enclosing the
body
and its contained lever and spring. This shell
will be described herein as comprising an inner
shell and a partially surrounding outer shell,
3 5 with the outer shell being generally the more
distal of the two.
3.3 In a widely used form, the catheter assembly includes
a
flexible catheter
cannula or sheath,
attached to
a base containing
a tapered internal
bore, which
is used for
the attachment
of other
CEO devices afterthe catheter has been inserted into the patient.
For
use with this invention, this internal bore has an annular
groove
formed in its wall near the larger, proximal, or entry end
of the
bore.
3
20~~~~~
3.4 The outer shell of this invention includes an axial
extension from its distal end of generally cylindrical form,
which extends into the tapered bore of the catheter hub, reaching
past the annular groove formed therein. This axial extension,
referred to hereinafter as the retaining plug, has a central
axial internal bore to accommodate the insertion needle, and is
divided into a plurality of cylindrical sectors by longitudinal
radial slots formed therein, with the slots extending into the
larger proximal portion of the outer shell. These slots divide
the cross-section of the outer shell so as to impart radial
flexibility to the cylindrical sectors of the retaining plug,
which can flex in cantilever from their attachment ~co the
unslotted proximal portion of the outer shell.
3.5 Each sector of the retaining plug carries on its outer
cylindrical surface a barb. The longitudinal section of each
barb may typically resemble a so-called buttress thread, or more
familiarly, one half of an arrowhead, with the arrow pointing
distally along the needle axis.
3.6 The dimensions of the retaining plug and the barbs are
such as to allow free axial passage of the barbs within the
proximal portion of the internal bore of the catheter hub, when
the retaining plug alone is inserted therein.
3.7 Each barb on the retaining plug is located so as to fit
into the annular groove in the catheter hub when the retaining
plug is expanded radially by the axial insertion of a suitable
cylindrical expansion member into the central cylindrical bore of
the retaining plug. With the retaining plug thus expanded, it is
retained axially within the catheter hub by the engagement of the
barbs with the annular groove in the hub.
3.8 The above expansion member, referred to hereinafter as
a spigot, consists of a substantially cylindrical axial extension
of the distal end of the body of the needle guard mechanism.
3.9 Prior to use of the catheter assembly, the needle guard
is held in the unlocked state by the presence of the needle shaft
within the needle guard body, with the needle holding the sensing
plate of the lever against the urging of the spring in a position
radially removed from the needle axis. This is described more
fully in the cited prior applications. A radial extension of the
sensing plate engages the distal end face of the inner shell,
holding the lever and the body axially at the distal end of the
cylindrical internal cavity of the shell.
3.10 In this position of the body, the spigot of the latter
is held in position inside the internal bore of the retaining
plug, so as to expand it into locking engagement with the
catheter hub as described in 3.7 above.
50243 910603 4
20~~~~~
3.11 On withdrawal of the needle following insertion of the
catheter, the passage of the needle tip past the sensing plate of
the lever allows the sensing plate to move radially inward under
urging of the spring, initiating the locking action of the needle
guard, as described in the cited prior applications.
3.12 This inward motion of the sensing plate disengages the
latter from the end face of the inner shell, allowing axial
motion of the lever and body in a proximal direction within the
internal cavity of the shell. This motion withdraws the spigot
from the internal bore of the retaining plug, allowing it to
collapse inwardly, disengaging the barbs from the groove in the
internal bore of the catheter hub. This allows separation of the
needle guard from the catheter, completing the operational
sequence for the device.
4. SUMMARY OF THE FIGURES
4.1 Figure 1 is a longitudinal sectional view of a needle
guard employing a canted-plate locking lever, as described in the
cited prior applications, and installed on an intravenous
catheter assembly. The assembly is shown in its pre-use or
unlocked state.
4.2 Figure 2 is a detail view of the outer shell of the
needle guard, shown in longitudinal section.
4.3 Figure 3 is an exterior top view of Figure 2.
4.4 Figure 4 is an exterior distal end view of Figure 2.
4.5 Figure 5 is an exterior proximal end view of Figure 2.
4.6 Figure 6 is a longitudinal sectional view of the needle
guard of Figure 1, shown in its after-use or locked state, with
the needle guard locked over the needle tip and almost completely
withdrawn from the catheter hub.
4.7 Figure 7 is a partial longitudinal sectional view of
the junction between the needle guard and the catheter hub
immediately following locking of the guard but before removal of
the guard from the catheter hub.
5. DESCRIPTION OF THE PREFERRED EMBODIMENTS
5.1 In Figure 1 is shown a typical intravenous catheter
assembly, comprising flexible cannula 601 mounted in catheter hub
602, and insertion needle 603 mounted in needle base 604. The
needle is shown fully inserted in the assembly in its pre-use
state, with the needle tip 605 extending slightly beyond the
50243 910603 5
2~4~~~0
cannula tip 606 in the usual way.
5.2 The needle guard assembly comprises body 607, lever
608, spring 609, inner shell 6.10, and outer shell 611. The
latter two shell portions are typically held together by snap
connection 631.
5.3 The operation of the needle guard in sensing the entry
of the needle tip 605 into the guard body and the subseguent
locking action are described in the cited prior applications.
5.4 In the unlocked state as shown, spring 609 presses
against the lower end of locking plate 612 of lever 608, causing
it to tend to pivot counter-clockwise about its upper point of
contact 613 with the sloped internal face 614 of body 607. This
rotation is prevented by sensing plate 615 at the opposite end of
lever 608 coming into contact with needle 603 at point 616.
5.5 With sensing plate 615 positioned as shown, lever 608
is restrained from moving to the right relative to the shell by
the upper end of plate 615 coming in contact with end face 617 of
inner shell 610.
5.6 The reaction of spring 609 acting against the immovable
lever 608 presses body 607 to the left against internal face 618
of outer shell 611, thus holding spigot 619 in bore 620 of
retaining plug 621.
5.7 Referring to Figures 2, 3, 4, and 5, which depict outer
shell 611 in isolation, retaining plug 621 extends from the
closed left end of the outer shell, and is divided into three or
more sections by slots 622, which extend into the larger portion
of the outer shell to point 623. The shell is molded of a
suitable compliant plastic material.
5.8 These longitudinal sections of shell function as
cantilever beams, able to flex radially from their point of
common attachment to end 624 of the outer shell 611. Dy applying
internal expansion 625 to the internal bore 620 of retaining plug
621, the latter may be expanded in the directions 626.
5.9 Referring to Figure 1, spigot 619 holds retaining plug
621 in an expanded state, so that barbs 627 engage annular groove
628 in the wall of catheter hub 602. This holds retaining plug
621 axially in the tapered bore 629 of catheter hub 602.
5.10 During withdrawal of the needle following insertion of
the cannula, the retaining plug 621 is maintained in the expanded
state by spigot 619, until the needle tip 605 reaches the
proximal side of sensing plate 615, as shown in Figure 6. This
removes the radial restraint from point 616 at the lower end of
sensing plate 615, allowing spring 609 to rotate lever 608 in a
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CA 02044818 2003-O1-23
counter-clockwise direction about its pivot point 613, to
assume the locked position shown. The accompanying locking
action is fully described in the cited prior applications.
5.11 With sensing plate 615 in its locked position as
shown in Figure 6, its upper end no longer engages end face
617 of inner shell 610. This frees lever 608 to follow the
continued withdrawal motion of needle 603 to the right, and
this motion is imparted through pivot point 613 to body 607,
moving it to the right in the cavity 630 of inner shell 610.
7_0 5.12 The rightward motion of body 607 withdraws spigot
619 from internal bore 620 of retaining plug 621, allowing
the latter to collapse inwardly because of its intrinsic
compliance, and disengaging barbs 627 from groove 628 in
catheter hub 602. This allows the entire needle guard
7_5 assembly to be withdrawn from the catheter hub as shown, to
be disposed of along with the needle.
5.13 Spigot 619 may be formed with a slight taper, with
the diameter diminishing in the distal direction. This will
allow the inwardly-collapsing effort of the several
?0 compliant sections of retaining plug 621 to assist the
effort of withdrawing the spigot from retaining plug 621.
The taper may be made sufficiently steep that the spigot can
be ejected entirely by this inwardly-collapsing action,
without requiring any further withdrawal effort by the user.
25 5.14 To ensure that the needle guard releases freely
from the catheter hub after the needle guard locks,
retaining plug 621 must be held centered in the internal
bore 629 of the catheter hub 602, so that barbs 627 do not
catch on the edge of groove 628 during withdrawal. As shown
30 in partial view Figure 7, this alignment is obtained by the
engagement of a short cylindrical overhang 632 on the distal
end of outer shell 611 with a mating cylindrical shoulder
633 on the proximal end of catheter hub 602, when spigot 619
has withdrawn from the internal bore 620 of retention plug
a5 621, and the outer shell has collapsed inwardly. This
radial alignment is maintained until the barbs 627 have been
axially withdrawn out of alignment with groove 628, and
therefore can no longer accidentally engage the groove, as
shown in Figure 6.
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