Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Attorney Docket No. 11531
DENTAL SYRINGE HAVING A MEDICATION FLLLED CARPULE
AND A RETRACTABLE NEEDLE CANNULA
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a reusable, carpule
based dental syringe having a double ended cannula which is
to be retracted within a compact enclosure to permit the
safe handling and disposal of the cannula while avoiding an
accidental and possibly life threatening needle stick.
2. Background Art
Dental syringes of the type having a pre-filled
carpule of fluid medication and a double ended hypodermic
needle cannula are well known in the art for injecting such
medication from the carpule to a targeted tissue area of a
patient. However, at the completion of the injection, the
needle cannula is typically locked in an axially extended
position projecting outwardly from a distal bore formed
through the syringe cylinder.
In some cases, the syringe may be used to treat a
patient having a communicable disease. Prior to disposing
the syringe, the needle cannula is frequently broken or
destroyed to prevent reuse. Dental office workers are
especially susceptible to accidental and potentially
infectious needle sticks due to the careless handling or
breaking of the needle and disposing of the syringe after
use. The resulting mini-accident caused by an accidental
needle stick typically requires a blood test for such
diseases as AIDs and hepatitis. The corresponding cost and
inefficiency of testing dental office workers who have
received such an accidental needle stick result in
considerable waste, which may be particularly damaging to a
dental facility which is striving for economy.
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The following U.S. patent and application, which
have been or will be assigned to the assignee of the present
invention disclose carpule based dental syringes having a
retractable needle cannula and a flexible locking arm for
controlling the movement of said carpule relative to the
cylinder of the syringe: U.S. Patent No. 4,767,413 issued
August 30, 1988 and U.S. Patent Application No. 135,607
filed December 21, 1987.
SUMMARY OF THE INVENTION
In general terms, a reusable dental syringe is
disclosed including a hollow cylinder having an open
proximal and distal ends and an axially aligned hollow body
portion. A conventional medication filled carpule is pushed
through a hollow carpule adapter for receipt by a movable
needle carrier at the distal end of the adapter, and the
combination carpule and adapter are loaded into the cylinder
through a longitudinally extending opening therein. A
conventional hub supported, double ended needle cannula is
attached to the needle carrier via the open distal end of
the cylinder so as to penetrate the carpule and communicate
with the interior thereof. A hollow control rod is advanced
distally, against the bias of a helical compression spring,
through the hollow body of the syringe and the open proximal
end of the syringe cylinder so that a retaining sleeve at
one end of the control rod will be correspondingly advanced
into surrounding engagement with the proximal end of the
carpule to prevent displacement of the carpule relative to
the cylinder. A flexible spring arm, which carries a
release button at one end thereof, is attached to and
movable with the control rod until the release button pops
through a hole in the syringe body to lock the control rod
at its distally advanced position. A piston stem is
slidable distally through the hollow control rod to be
connected to and control the movement of a piston through
the carpule so that medication may be expulsed from the
carpule via the needle cannula.
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In operation, the dentist locates the needle
cannula at a targeted tissue area of the patient and slides
the piston stem distally through the hollow control rod and
into the carpule. The distal movement of the piston stem
drives the piston through the carpule to administer an
injection of the medication into the targeted tissue. Upon
completing the injection, and while holding the carpule
against axial displacement, the dentist presses the release
button of the spring arm through the hole in the syringe
body to release the control rod from its distally advanced
position, whereby the formerly compressed spring is now free
to return to the relaxed condition. The control rod and
piston stem are then withdrawn rearwardly through the
syringe body and away from the carpule, such that the
retaining sleeve of the control rod is moved out of
engagement with the carpule and the piston stem is
disconnected from the piston.
The combination carpule and carpule adapter are
rotated downwardly, around an enlarged end of the adapter,
through the longitudinally extending opening in the syringe
cylinder. Next, the dentist grasps and pulls the carpule
rearwardly through the adapter to correspondingly relocate
the movable needle carrier and the needle cannula attached
thereto towards the proximal end of the adapter. The needle
carrier is anchored in its relatively proximal position by
means of locking detents located at the proximal end of the
adapter to prevent any further displacement of the needle
cannula. Accordingly, the needle cannula is retracted into
and surrounded by the carpule adapter to form a safe and
compact package which is suitable for disposal and in which
the cannula is rendered irretrievable and non-reusable to
thereby avoid an accidental needle sticlc and the possible
spread of disease.
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BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a partially exploded view of the
dental syringe which forms the present invention;
FIGS. 2 and 3 show partial cross-sections of a
carpule adapter which is to be interfaced with a
conventional medication filled carpule and loaded into the
cylinder of the dental s~ringe of FIG. 1;
FIG. 4 is a cross-section of the dental syringe in
a pre-injection state;
FIGS. 5-7 are cross-sections of the dental syringe
in an injection state where medication is expulsed from the
carpule to a targeted tissue area via a conventional double
ended needle cannula;
FIG. 5' is a cross-section taken along lines 5'-
5' of FIG. 5;
FIG. 8 is a cross-section of the dental syringe
which illustrates an optional step of temporarily retracting
the needle cannula into the syringe cylinder if an injection
is to be administered in step-wise increments;
FIG. 9 is a cross-section of the dental syringe in
a post-injection state; and
FIGS. 10-12 illustrate the retraction and
anchoring of the needle cannula within the cannula adapter
to form a compact package suitable for handling and disposal
in which the cannula is rendered irretrievable and
nonreusable.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The carpule based, reusable dental syringe 1 of
the present invention is now described in detail while
referring to the drawings, where FIG. 1 shows a partially
exploded view of the syringe 1 and a combination carpule 2
and carpule adapter 4. Carpule 2, which is typically formed
from glass or other transparent material, is of conventional
design and includes a rubber piston 3 located at the
proximal end thereof. Carpule 2 is filled with a supply of
fluid medication, such as novocaine, or the like. The
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details of carpule adapter 4 will be described when
referring to FIGS. 2 and 3.
The syringe 1 includes a hollow cylinder or barrel
6 having open proximal and distal ends, a longitudinally
extending opening 8 formed through one side of the cylinder
(for removable receipt of the combination carpule 2 and
adapter 4), and a longitudinally extending window 10 formed
through the opposite side (for gaining visible access to the
medication filled carpule when such carpule is loaded into
the interior of hollow cylinder 6). Coextensively joined to
and axially aligned with the cylinder 6 is a hollow body
portion 12. Located within the body portion 12 of syringe 1
is a helical compression spring (designated 14 in FIG. 4).
Projecting radially outward in opposite directions from the
body portion 12 is a pair of finger ledgeq 16. A hole 18
(best illustrated in FIG. 4) is formed through one side of
body portion 12 between the oppositely extending finger
ledges 16. The purpose of hole 18 for receiving a spring
biased button 54 therethrough will be described later when
referring to FIG. 4.
A hollow control rod (designated 20 in FIG. 4) is
slidably received in and adapted for axial and reciprocal
movement through the hollow body portion 12 of syringe 1.
Affixed to one end of the control rod 20 is a disk-like
arming flange 22. Affixed to the opposite end of control
rod 20 is a hollow retaining sleeve 24. As will soon
explained, a force for moving the control rod 20 distally
through hollow body portion 12 is applied to the arming
flange 22, whereby to correspondingly advance retaining
sleeve 24 (against the bias of compression spring 14)
through the open proximal end of cylinder 6 for surrounding
and engaging the proximal end of carpule 2. A flexible
spring arm (designated 52 in FIG. 4) is attached to and
movable with the control rod 20 to releasably lock the
control rod in a relatively distal position with the
retaining sleeve 24 thereof securely engaging the carpule 2
for a purpose that will soon be described.
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A piston stem 26 is slidably received in and
adapted for axial and reciprocal movement through the hollow
control rod 20, such that piston stem 26 is coaxially
aligned with each of the body portion 12, compression spring
14 ~of FIG. 4), and control rod 20 (also of FIG. 4).
Affixed to one end of piston stem 26 is a thumb ring 28, and
affixed to the opposite end of stem 26 is a sharp-edged
harpoon 30. As will soon be explained, the movement of
piston stem 26 in a distal direction through hollow control
rod 20 is manually controlled at the thumb ring 28, whereby
to correspondingly advance harpoon 30 for connection to the
piston 3 of carpule 2 so that said piston can be driven
through the carpule for expulsing the fl~lid medication
therefrom.
Syringe 1 is associated with a conventional double
ended hypodermic needle cannula 32. Cannula 32 is affixed
to a screw threaded hub 34 and is adapted to communicate
with the carpule 2 at the interior of cylinder 6 by way of
the carpule adapter 4. That is to say, in the assembled
relationship (of FIG. 4), needle hub 34 is connected to
adapter 4 via the open distal end of cylinder 6, such that
one end of cannula 32 projects inwardly into the cylinder 6
to penetrate the carpule 2, and the opposite end of cannula
32 projects outwardly from the cylinder 6 to deliver the
medication during the administration of an injection.
More particularly, and referring concurrently to
FIGS. 1-3 of the drawings, the carpule adapter 4 includes a
hollow, open ended tube-like body having a diameter which is
sized to receive the medication carpule 2 therewithin. A
plurality of evenly spaced, longitudinally extending tracks
38 are formed through the body of adapter 4. Located at the
rearward or proximal end of each track 38 and spaced axially
from one another is a stop 40 and a locking detent 42. The
purpose of stops 40 and locking detents 42 will soon be
described. The forward or distal end of adapter 4 includes
a head portion 44 having a slightly enlarged diameter
relative to the tube-like body for the dual purpose of
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creating a reliable snap fit of the adapter 4 within the
syringe cylinder 6 while also establishing a pivot surface
for permitting adapter 4 to rotate outwardly from the
cylinder to achieve an important advantage that will be
disclosed hereinafter when referring to FIG. 10.
A needle carrier 46 is located in and movable
through the hollow interior of carpule adapter 4. Needle
carrier 46 includes a generally hollow body and a plurality
of radially projecting latches 48 which are received within
and slidable through respective tracks 38 of adapter 4. As
shown in FIG. 2, the needle carrier 46 is initially
positioned forwardly in the adapter 4 and at the distal end
thereof so that when the carpule 2 is inserted into the
adapter, the end cap of the carpule will be received by and
attached to the needle carrier. The needle carrier 46 also
includes a screw threaded bore 50 which, after carpule 2 has
been inserted into adapter 4 and the combination carpule and
adapter have been loaded into the syringe cylinder 6 through
opening 8, is adapted to be mated to the screw threaded hub
34 via the open distal end of cylinder 6. Thus, the
inwardly projecting end of needle cannula 32 will extend
through the bore 50 of needle carrier 46 to penetrate the
carpule 2 at the interior of carpule adapter 4 (best shown
in FIG. 63.
As shown in FIG. 3, when the needle carrier 45
slides rearwardly towards the proximal end of adapter 4, the
latches 48 ride through tracks 3~ until such latches are
received in the spaces between stops 40 and locking detents
42. The latches 48 are thereby permanently retained between
stops 40 and detents 42 to blocX any further displacement of
needle carrier 46 through adapter 4 and thereby anchor said
needle carrier at the proximal end of the adapter, the
advantage of which will be described when referring to FIG.
11 .
Referring now to FIG. 4 of the drawings, the
dental syringe l is shown in the pre-injection state after
the carpule has been inserted into and pushed fon~ardly
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through the carpule adapter 4 and the combination carpule
and adapter have been loaded into the syringe cylinder 6,
such that the relatively large head 44 of adapter 4 is
detachably snap-fit within the cylinder. As previously
indicated, the needle carrier 46 is initially positioned at
the distal end of adaptar 4 to receive the end cap of the
carpule 2 below the bore 50.
As was also earlier indicated, a flexible spring
arm 52 is connected at one end thereof and movable with the
control rod 20. Projecting radially from the opposite end
of spring arm 52 is a release button 54 which is aligned and
sized for receipt within a hole 58 through the body portion
12 of syringe 1 (best illustrated in FIG. 5) for the purpose
of locking control rod 20 in a relatively distal relative to
said body portion. However, in the pre-injection state of
FIG. 4, the control rod 20 is in a proximal position
relative to body portion 12, and the compression spring 14
which surrounds the control rod within body portion 12 is in
a relaxed, expanded condition. Therefore, the arming flange
22 of control rod 20 is spaced axially from body portion 12,
and the retaining sleeve 24 is spaced proximally from the
carpule 2, such that release button 54 of spring arm 52 is
positioned rearwardly of and out of engagement with the hole
18. Moreover, the piston stem 26 is located rearwardly of
the control rod 20, such that the harpoon 30 thereof is also
spaced rearwardly of and out of contact with the piston 3 of
carpule 2.
The operation of the dental syringe 1 is now
described while referring to FIGS. 5-9 of the drawings.
Referring first to FI~. 5, an axially directed force is
manually applied by the dentist (in the direction of the
reference arrow 56) to the arming flange 22 of control rod
20, whereby to move the control rod, against the bias of
compression spring 14, distally through the hollow body
portion 12 of syringe 1. The flexible spring arm 52 of
control rod 20 is, likewise, moved distally through body
portion 12 and slightly bent therein until release button 54
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pops through hole 18 to lock the control rod and thereby
prevent any further displacement thereof relative to body
portion 12. Accordingly, the compression spring 14 is held
in a compressed state at the distal end of body portion 12.
What is more, the retaining sleeve 24 of control rod 20 is
also moved distally through body portion 12 and into the
syringe cylinder 6 via the open proximal end thereof ~o as
to surround and engage the proximal end of carpule 2 and
thereby secure said carpule against movement relative to the
cylinder.
As a preferred embodiment of the present
invention, and referring concurrently to FIGS. 5 and 5', a
ring-shaped elastomeric (e.g. rubber) liner 58 extends
around the interior periphery of the retaining sleeve 24 of
control rod 20. The liner 58 includes a series of evenly
spaced, radially inward extending projections 60 which
establish a tight friction fit against the carpule 2 when
the retaining sleeve 24 is advanced through the body 12 of
syringe 1 to surround and engage the proximal end of said
carpule. In this manner, the projections 60 of liner 58 may
be slightly compressed to permit retaining sleeve 24 to
firmly grasp carpule 22 and thereby assure that a subsequent
rearward relocation of the control rod 20 through body
portion 12 will cause a corresponding rearward relocation of
the carpule 2 through cylinder 6 (in a manner to be
described when referring hereinafter to FIG. 8).
FIGS. 6 and 7 of the drawings illustrate the
dental syringe in the injection state. More particularly,
and referring to FIG. 6, with the control rod 20 advanced to
and locked at a relatively distal position and the carpule 2
secured within the syringe cylinder 6 by retaining sleeve
24, the dentist applies an axial force (in the direction of
the reference arrow 64) to the thumb ring 28 of piston stem
26 to advance stem 26 distally through the hollow control
rod 20 until the harpoon 30 penetrates the piston 3 of
carpule 2 at the proximal end of cylinder 6. Accordingly, a
piston assembly is formed comprising the interconnection of
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piston s~em 26 to piston 3. Next, a conventional double
ended hypodermic needle 32, which is affixed to and
supported by a conventional screw threaded hub 34, is
interfaced with carpule 2 via the open distal end of
cylinder 6. More particularly, the screw threaded hub 34 is
mated to the screw threaded bore 50 of needle carrier 46 at
the distal end of carpule adapter 4, such that the inwardly
projecting end of cannula 32 penetrates the carpule to
communicate the fluid contents thereof, and the outwardly
projecting end o~ cannula 32 extends outside the cylinder 6
for administering an injection of said contents.
In FIG. 7, an injection is administered by syringe
1 in a medically accepted fashion. That is to say, the
dentist first locates the outwardly projecting end of needle
cannula 32 at a targeted tissue area of the patient. The
dentist then resumes the application of the axial force to
the thumb ring 28 of piston stem 26, whereby to continue the
distal displacement of piston stem 26 through hollow control
rod 20 for correspondingly driving the piston 3 through the
carpule 2. The distal relocation of piston 3 through the
carpule 2 expulses a suitable volume of fluid medication to
the patient via the needle cannula 32.
FIGS. 8 and 9 show the dental syringe in the post-
injection state after an injection has been either partially
(in FIG. 8) or fully (in FIG. 9) administered and the needle
cannula has been removed from the patient's tissue. In FIG.
8, the needle cannula 32 is shown temporarily retracted
within the syringe cylinder 6 to avoid an accidental needle
stick prior to a resumption and completion of the injection.
By way of example, it may be desirable to retract cannula 32
temporarily if the dentist wishes to momentarily lay the
syringe in a dental tray and thereby administer the
injection incrementally in two or more successive steps. In
this case, the dentist depresses the release button (shown
in phantom and designated 54-1) against the bias of spring
arm 52 to move the button inwardly of its hole 18 and
thereby bend spring arm 52 in a radially inward direction.
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11
The depression of release button 52 through hole 18 unlocXs
the control rod 20 from its distally advanced position
relative to the body portion 12 of syringe 1. The
compression spring 14 is now free to return to its normal,
expanded state, such that the stored potential energy within
spring 14 will automatically and simultaneously drive
control rod 20 and piston stem 26 in a proximal direction
tas indicated by the reference arrow 66) through body
portion 12. The proximal movement of control rod 20 and
piston stem 26 correspondingly causes the carpule 2 to be
relocated proximally through cylinder 6 for receipt within
body portion 12 (via the open proximal end of the cylinder),
whereby cannula 32 is safely retracted into the cylinder 6.
When the dantist later wishes to complete the
injection, he once again applies an axial force to the
arming flange 22 of control rod 20 to advance the control
rod 20 and piston stem 26 distally through body portion 12
to return carpule 2 and cannula 32 to the injection state of
FIG. 7. The piston 3 is then driven through the carpule 2
by means of piston stem 26 to expulse all (or another
portion) of the remaining fluid medication. Of course, if
all of the fluid were to be initially expulsed from carpule
2 during a single, continuous step, such that the temporary
retraction of cannula 32 into cylinder 6 would not be
needed, then the post-injection steps described with
reference to FIG. 8 may be avoided.
In FIG. 9, the injection has now been completed so
that the needle cannula 32 can be safely and permanently
retracted into the carpule adapter 4. More particularly,
the dentist uses his thumb` and forefinger to grasp the
proximal end of carpule 2 (by way of the opposing opening 8
and window 10 through the cylinder 6) to thereby prevent the
relocation of the carpule relative to the cylinder. Next,
the dentist depresses the release button 54, whereby move
the button inwardly and against the bias of spring arm 52
through the hole 18 to unlock the control rod 20 from its
distally advanced position and permit compression spring 14
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12
to return to the expanded state (in the manner described
while referring to FIG. 8).
While maintaining a firm grasp on carpule 2 with
one hand, the dentist uses his opposite hand to grasp and
pull the arming flange 22 of control rod 20 in a rearward
direction (as indicated by the reference arrow 68). Pulling
the arming flange 22 in a rearward direction correspondingly
causes the control rod 20 and the retaining sleeve 24
thereof to be relocated proximally through the hollow body
portion 12 of syringe 1. Therefore, the retaining sleeve 24
which previously surrounded and engaged the proximal end of
the carpule 4 is now disengaged from said carpule to permit
the carpule to be displaced relative to the syringe cylinder
6. The proximal relocation of the control rod 20 also
displaces piston stem 26, whereby to detach the harpoon 30
from piston 3. The piston stem 26 may then be withdrawn
from the carpule 2 by means of pulling the finger ring 28 in
a rearward position.
FIGS. 10 and 12 of the drawings illustrate the
removal of the combination carpule 2 and carpule adapter 4
from the syringe cylinder 6 and the retraction of the needle
cannula 32 into the adapter. In FIG. 10, after the control
rod 10 and piston stem 26 have been relocated proximally
through the hollow body portion 12 of syringe 1, whereby
carpule 2 can be displaced relative to the cylinder, the
syringe 1 is turned so that the opening 8 through cylinder 6
faces downwardly. The combination carpule 2 and carpule
adapter 4 are pivotally supported within cylinder 6 at the
enlarged head 44 of adapter 4 so as to rotate, under the
influence of gravity, downwardly and outwardly from the
cylinder via the opening 8 therethrough.
In FIG. 11, with the carpule adapter 4 still
pivotally supported within cylinder 6 at the enlarged head
44 of the adapter, the dentist grasps the carpule 2 and
applies a proximal pulling force thereto (in the direction
indicated by the reference arrow 70). Accordingly, the
carpule 2 and needle carrier 46 attached thereto slide
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proximally through adapter 4, such that the latches 48 of
carrier 46 ride through respective longitudinally extending
tracks 38 in adapter 4 until each latch 48 is seated in the
space between a stop and a locking detent (designated 40 and
42 and best shown in FIG. 3) to prevent any further
displacement of needle carrier 46. The needle carrier 46 is
thereby anchored at the proximal end of adapter 4 with the
needle cannula retracted completely within and surrounded by
said adapter.
In FIG. 12, the dentist continues to apply a
proximal pulling force to carpule 2 until the carpule
adapter is separated from its pivotal attachment to the
syringe cylinder 6. Accordingly, a compact disposal package
is now available consisting of the empty carpule 2 pulled
rearwardly through and locked (by means of anchoring the
needle carrier 46) within the carpule adapter 4. What is
more, the needle carpule 32 is irretrievably located within
adapter 4 so as to be rendered inaccessible and non-
reusable. Therefore, the disposal package may be safely
handled and discarded while avoiding the possibility of an
accidental needle stick and the threat of spreading a
contagious, and conceivably life threatening, disease. The
dental syringe 1 of the present invention is then ready for
sterilization and reuse with a fresh medication filled
carpule, carpule adapter, and needle cannula in the manner
that has been described aboveO
It will be apparent that while a preferred
embodiment of the invention has been shown and described,
various modifications and changes may be made without
departing from the true spirit and scope of the invention.
For example, although the syringe 1 has been described as
having particular application as a dental syringe, it is to
be understood that this is not to be regarded as a
limitation of the claimed invention. That is, the syringe l
is also adapted for any other use where a fluid is to be
injected from a prefilled carpule.
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14
Having thus set forth a preferred embodiment of
the present invention, what is claimed is:
