Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~3~ 5~
This invention relates to a disposable
safety syringe, such as a dental syringeJ having a
pre-filled fluid medication cartridge and a double-
ended hypodermic needle cannula, and, more
particulaxly, to means by which the needla cannula may
be relocated from an axially extended position, at
which to inject the fluid contents of the medication
cartridge into a targeted tissue area, to a retracted
position, at which the cannula is withdrawn into and
completely shielded by the medication cartridge at the
interior of the syringe cylinder.
Dental syringes of the type having a pre-
filled cartridge of fluid medication and a double-
ended hypodermic needle are well-known in the art for
injecting such medication ~rom the cartridge to a
targeted tissue area of a patient. However, at the
completion of the injection, the needle is tvpically
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 hypodermic needle is
frequently broken or destroyed to prevent reuse.
Dental office workers are especially susceptable to
accidental and potentially infectious needle strikes
due to the careless handling or ~reaking of the needle
~3~
--2--
and disposing of the syringe after use. The resulting
mini-accident caused by an accidental needle strike
typically requires a blood test Por such disea~es as
AI~S and hepatitis. The corresponding cost and
inefficency of testing dental office workers who have
received such an accidental needle strike result in
considerable waste, which may be particularly damaging
to a dental facility which is striving for economy.
Briefly, the present invention relates to a
di5posable safety syringe, such as a dental syringe,
or the like, by which a hypodermic needle cannula may
be retracted into an evacuatPd medication cartridge at
the interior of the syringe cylinder so as to prevent
reuse of the syringe and permit the syringe to be
safely handled and discarded without subjecting health
care workers to an accidental needle strike and the
spread of a contagious and, possible life threatening,
disease. According to a first embodiment of the
invention, the syringe includes a hollow cylinder
- 20 having proximal and distal ends and a bore formed
through the distal end. A pair of inwardly projecting
needle retaining shoulders are hingedly connected to
the distal end of the cylinder to define a bore
therebetween. A double-ended needle cannula extends
through and is retained within the distal bore by
means of a thermal bond to prevent movement of the
cannula relative to the bore. A first end of the
cannula extends into the interior of the cylinder, and
an opposite, second end of the cannula extends
outwardly from the cylinder for administering an
injection at a targeted tissue area.
A pre-filled fluid medication cartridge is
loaded into the cylinder through the proximal end so
as to be spaced axially from the first end of the
needle cannula. The cartridge contains a piston which
is movable through the cartridge to expulse the fluid
contents. A combination needle sheath/piston stem has
~3~
--3--
a relatively wide sleeve formed at one end and a pair
of flexible gripping arms projecting axially from the
opposite end. Initially, the wide sleeve of the
needle sheath/piston stem surrounds and sheaths the
second end of the needle canmlla to prevent the
contamination thereof and avoid an accidental needle
strike.
In operation, the medication cartridge is
advanced distally through the syringe cylinder until
the first end of the needle cannula penetrates the
cartridge to communicate with the fluid contents
thereof. The second end of the cannula is unsheathed,
and the flexible gripping arms of the needle
sheath/piston stem are detachably connected to the
piston at the interior of the medication cartridge to
complete a piston assembly. An axial force is then
applied to the piston stem to correspondingly drive
the piston distally through the cartridge to expulse
the contents thereof via the cannula, such that the
piston is penetrated by the first end of the cannula.
After the medication cartridge has been emptied, the
axial force is reapplied to the piston stem to cause
the cartridge to move distally through the syringe
cylinder and into contact with the needle retaining
shoulders at the distal end of the cylinder. The
axial force is transferred from the cartridge to the
distal end of the cylinder, whereby to cause the
needle retaining shoulders to rotate relative to the
needle cannula and thereby break the bond formed
between the shoulders and the cannula. The distal
bore is thereby opened to release the cannula
therefrom. The piston stem then moves the piston
proximally through the cartridge to correspondingly
retract the cannula through the opened distal bore and
into th~ medication cartridge, wherein the cannula is
completely shielded and irretrievably located.
According to a second embodiment of the
`` ~3~P Ei3~5~3
invention, a medication cartridge is loaded into a
syringe cylinder having open proximal and distal ends.
A double-ended needle cannula is releasably retained
at the distal end of the cylinder in fluid
communication with the cartridge by and between a pair
of rotatable jaws. Each jaw has a respective contact
face by which to engage the cannula and an adjacent
beveled surface having a channel foxmed therein.
The medication cartridge :is emptied via the
needle cannula in the same manner described while
r ferring to the syringe of the first embodiment. An
axial force is then applied to the piston stem to
drive the empty cartridge distally through the syringe
cylinder and into contact with the needle retaining
jaws at the distal end of the cylinder. The axially
applied force is transferred from the cartridge to the
jaws, whereby to cause said jaws to rotate relative to
the needle cannula. Accordingly, the respective
contact faces of the jaws are moved out of engagement
with the needle cannula. The adjacent beveled
surfaces of the jaws are thereby rotated into face-to-
face alignment with one another so that the cannula is
received and floating freely within the respective
channels of the beveled surfaces. The piston stem
then moves the piston proximally through the empty
cartridge to retract the cannula through the channels
of the jaws and into the medication cartridge, wherein
the cartridge is completely shielded and irretrievably
located.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG.~.is an exploded view of the disposable
safety syringe which forms the present invention;
FIG. 2 is an enlarged detail of the syringe
of FIG. l;
FI~. 3 is a cross-section showing the
syringe of FIG. 1 in the assembled relationship;
FIG. 4 illustrates the operational step of
~ ~ 3~6~51~
--5--
moving a medication cartridge distally through the
syringe cylinder until a needle cannula penetrates the
cartridge at the int~rior of the syringe cylinder;
FIG. 5 illustrates the detachable connection
of a piston stem to a piston of the medication
cartridge by which the piston can be moved axially
through the cartridge;
FIGs. 6a and 6b illustrate enlarged details
for detachably connecting the piston stem to the
piston of FIG. 5;
FIG. 7 illustrates the operational step of
moving the medication cartridge distally through the
syringe cylinder and into contact with the distal end
o~ the cylinder for breaking the bond formed between
the needle cannula and a distal bore;
FIG. 8 illustrates the operational step of
moving the piston proximally through the medication
cartridge for retracting the needle cannula through
the distal bore and into said cartridge;
FIG. 9 is an isometric view of a disposable
safety syringe which forms a second embodiment of the
present invention;
FIG. 10 shows the syringe of FIG. 9 with a
needle cannula being engaged by and releasably
retained between a pair of rotatable jaws;
FIG. 11 is an end view taken along lines 11-
11 of FIG. 10;
FIG. 12 shows the syringe of FIG. 9 with the
rotatable jaws rotated out of engagement of the needle
cannula;
FIG. 13 is a cross-section taken along lines
13-13 of FIG. 12; and
FIG. 14 shows the syringe of FIG. 9 with the
needle cannula removed from the jaws and retracted
into a medication cartridge located within the
cylinder of the syringe.
3~i6~
DESCRIPTION OF THE P~EFERRED EMBQDIMENTS
The disposable saEety syringe 1 of the
present invention is best described while referring to
the drawings, where FIG. 1 illustrates an exploded
view of the syringe components. More particularly,
syringe 1 includes a hollow cylinder or barrel 2
having an open proximal end and a partially closed
distal end. A major flange 3 extencls around the open
proximal end of the syringe cylinder 2. A relatively
narrow flange 4 extends around the periphery of
cylinder 2 intermediate the proximal and distal ends.
~n integral, flexible sealing gasket 6 projeots
outwardly through the open proximal end of cylinder 2.
The details o~ gasket 6 will be described in greater
detail hereinafter when referring to FIG. 2. Proximal
and distal locking detents 8 and 10 project inwardly
from opposite sides of the cylinder 2. ~rhe functions
performed by locking detents 8 and lO will be better
described when referring to FIG. 3. Briefly, however,
a notch (best illustrated in FIG. 3~ is formed through
cylinder 2 around the top and sides o~ locking detents
8 and 10 to permit detents 8 and 10 to rotate slightly
in an outward direction relative to cylinder 2.
The distal end of cylinder 2 includes a
narrow bore 12 which receives and retains a double-
ended hypodermic needle cannula 18 to permit fluid to
be delivered from the syringe 1 to a taxgeted tissue
area of a patient. Needle cannula 18 includes a fluid
port 19 (best shown in FIG. 3) which enables
substantially all of the fluid from syringa 1 to be
injected into the targeted tissue area. The distal
bore 12 is defined by a pair of oppositely disposed
needle retaining shoulders 14 and 16 which, as will
soon be explained, are hingedly connected to the
distal end of cylinder 2 so as to be adapted ~or
rotation in an outward direction relative to the
cylinder tbest illustrated in FIG. 7).
~3~6~
--7--
A pre-filled medication cartridge or ampule
20 is of suitable size so as to be loaded into the
syringe cylinder 2 through the open proximal end
thereof so that the contents of cartridge 20 may be
delivered to the targ~ted tissue area via needle
cannula 18. Cartridge 20 is typically formed from a
transparent mat~rial (e.g. glass, or the like) and is
filled with a fluid medication, such as Novacaine, or
the like. A rubber seal 22 extends across a distal
end of cartridge 20, and a metal end cap 24 secures
seal 22 to the cartridge. A neck 25 of relatively
reduced diameter is formed around the periphery of
cartridge 20 below end cap 24. A piston 26 is located
at the proximal end of cartridge 20. Piston 26 is
slideable axially through the cartridge to e~pulse the
fluid contents thereof (via cannula 18). The piston
28 of cartridge 26 includes a proximally projecting
plug member 28, the purpose and advantage of which
will be described when referring to FIGs. 6a and 6b.
Syringe 1 also includes a combination needle
sheath and piston stem 30. The combination needle
sheath and piston stem 30 has a substantially hollow,
elongated body with a relatively wide sleeve 32 formed
at one end and a pair of oppositely disposed, flexible
gripping arms 34 projecting from the opposite end. A
small locating bump 36 projects outwardly from each
gripping arm 34. As is best shown in FIG. 3, the
combination needle sheath/piston stem 30 functions as
a needle sheath, such that sleeve 32 receives and
surrounds one end of the needle cannula 18. As is
best shown in FIG~ 5, needle sheath/piston stem 30
also functions as a piston stem, such that the pair of
gripping arms 34 are releasably connected to the
piston 26 of medication cartridge 20 to form a piston
assembly.
FIG. 2 shows an enlarged detail of the
flexible sealing gasket 6 which is inteqrally
: L3~
connected to the proximal end of syringe cylinder 20
More particularly, gasket 6 is hingedly connected to
cylinder 2 so as to be adapted for rotation from an
outwardly projecting position (as illustrated in FIG.
1) to an inwardly projecting position relative to the
interior of cylinder 2 (as shown in phantom and
designated by the reference numeral 6-l of FIG. 2).
The means and advantage for rotating sealing gasket 6
into the interior of cylinder 2 is now described while
referring to FIG. 3.
FIG. 3 shows the disposable sa*ety syringe 1
in an assembled configuration so as to be suitable for
packaging and shipment to health care workersO In the
assembled relationship, the needle cannula 18 is
retained within the distal bore 12 of syringe cylinder
2 by a thermal bond that is formed between the cannula
and the opposing needle retaining shoulders 14 and 16.
one end of cannula 18 extends proximally into the
interior of cylinder 2 and is adapted to penetrate the
seal of the medication cartridge 20. The opposite end
of cannula 18 extends distally and outwardly from the
cylinder 2 for injecting the contents of cartridge 20
into the targeted tissue area. The distally extending
end of needle cannula 18 is initially surrounded and
protected by the needle sheath 30 so as to preserve
the sterility of cannula 18 and prevent an accidental
needle strike. More particularly, the relatively wide
sleeve 32 of needle sheath 30 is placed over the
proximal end of cylinder 2 until a flanged end of
sheath 30 engages the intermediate flange 4 of
cylinder 2. It may be desirable to heat seal sleeve
32 to flange 4 to prevent a premature removal of
needle sheath 30 from cylinder 2.
The medication cartridge 20 is loaded
through the open proximal end of an advanced distally
through the syringe cylinder 2 until the proximal
locking detent 8 is received in a snap-fit engagement
13C~6~SB
g
within the neck 25 of cartridge 20. Accordingly,
cartridge ~0 is initi.ally retained within cylinder 2
in spaced, axial alignment with the needle cannula 18,
such that a small portion of the ca:rtridge 20 extends
outwardly from the proximal end of cylinder 2.
At the same time that medication cartridge
20 is loaded into the syringe cylinder 2, the flexible
sealing gasket 6 is engaged by cartridge 20 and
rotated from the outwardly projecting position of FIG.
l to the inwardly projecting position (represented by
reference numeral 6-1) of FIG. 2. That is, the distal
advancement of cartridge 20 through cylinder 2
automatically rotates gasket 6, so that an air-tight
seal is formed between cylinder 2 and cartridge 20 to
preserve the sterility of needle 18 by preventing
contaminated air from reaching cannula 18 via the
space between the cyli.nder 2 and the cartridge 20.
The operation of the syringe 1 of the
present invention is now described while referring to
FIGs. 4-8 of the drawings. In FIG. 4, the user places
his index and middle fingers under the major flange 3
of syringe cylinder 2 and his thumb against the end of
medication cartridge 20 which extends outwardly from
the cylinder 2 (best represented in FIG. 2). The user
then uses his thumb to exert and axial force upon the
medication cartridge 20 (in the direction of the
reference arrow) by which to rotate proximal locking
detent 8 out of engagement with the neck 25 of
cartridge 20 and thereby permit cartridge 20 to be
driven distally through cylinder 2. The continued
application of the axial force to cartridge 20 causes
the cartridge to slide through cylinder 2 until the
respective proximal ends of cartridge 20 and cylinder
2 lie adjacent one another and the proximally
extending end of cannula 18 penetrates the rubber seal
22 to communicate with the fluid contents of cartridge
20, 50 that an injection of the contents may be
~3~ 51~
.,~
--10~
subsequently administerPd. Accordingly, the distal
locking detent 10 is received in a snap-fit engagement
within the neck 25 of cartridge 20, and the cartridge
20 is retained in spaced proximity to the needle
retaining shoulders 1~ and 16 at the distal end of
syringe cylinder 2.
In FIG. 5 of the drawings, the user removes
the needle sheath/piston stem 30 to unsheath the
distally extending end of needle cannula 18. The user
then grasps the cylinder 2 of syringe 1 with one hand
and uses his opposite hand to attach needle
sheath/piston stem 30 to the piston 26 of medication
cartridge 20 to complete a piston assembly comprising
a piston head 25 and an elongated piston stem 30.
More particularly, and reférring
concurrently to FIGs. 5 and 6 of the drawings, the
user applies an ax:ial force (in the direction of the
reference arrow in FIG. 5) to the piston stem 30 to
move the flexible gripping arms 34 through the
proximal end of medication cartridge 20 and adjacent
the plug member 28 of piston 26. As is best shown in
FIG. 6a, each gripping arm 34 terminates at an
inwardly projecting retaining finger 40. As the
piston stem 30 is moved through the cartridge 20 ~in
the manner illustrated in FIG. 6b) to drive the piston
26 distally through the cartridge, the locating bumps
36 of gripping arms 34 will contact the interior walls
of cartridge 20, whereby to cause the flexible
gripping arms 34 to rotate inwardly towards plug
member 28~ A rotation of the gripping arms 34
correspondingly causes the inwardly projecting
retaining fingers 40 to be rotated into engagement
with and releasably retained by a relatively narrow
neck 42 formed around the plug member 28 of piston 26.
Therefore, so long as the locating bumps 36 on
gripping arms 34 of piston stem 30 are located within
the interior of medication cartridge 20, the retaining
3~6~
11--
fingers 40 will be held within the neck 42 of plug
member 28 to prevent the detachment of piston stem 30
from piston 26~
In FIG. 7 of the drawings, the user
administers an injection by keeping his index and
middle fingers located behind the major flange 3 of
cylinder 2 and relocating his thumb to the sleeve 32
of piston stem 30. The user then applies an axial
force to sleeve 32 (in the direction of the reference
arrow) to drive the piston 26 distally through
medication cartridge 20 to expulse the fluid contents
thereof through the needle 18 and into the targeted
tissue area o~ the patient. It may be noted that by
virtue of the fluid port 19 in cannula 18,
substantially all of the fluid may be expulsed from
cartridge 20 as the piston 26 is advanced to the
distal end of the cartridge. Moreover, the proximally
extending end of the needle cannula 18 penetrates and
is thereby connected to piston 26 when the piston is
moved completely through cartridge 20 to expulse the
fluid therefrom.
Once the medication cartridge 20 has been
emptied and the injection completed, the user
continues to apply an axial force to the sleeve 32 of
piston stem 30. Accordingly, the piston 26 (which has
already been driven to the distal end of cartridge 20)
transfers the axially applied force to the cartridge,
so as to cause the distal locking detent 8 to rotate
out of engagement with the necX 25 of cartridge 20 and
thereby permit an additional distal movement of the
cartridge through the syringe cylinder 2. The
continued application of the axially applied force to
sleeve 32 advances medication cartridge 20 distally
through cylinder 2 until the metal end cap 24 thereof
is moved into contact with needle retainin~ shoulders
14 and 16. The axially applied force is then
transferred from the cartridye 20 to the inwardly
~3~
-12~
projecting needle retaining shoulders 14 and 16 to
cause said shoulders to rotate (in the direction o*
the reference arrows) around their respecti~e integral
(i.e. living) hinge~ ak the distal end oP cylindex 2
to thereby break the thermal bond between needle
cannula 18 and shoulders 14 and 16~ With the bond
broken and the neadle 18 no longer r~tained between
shoulders 1~ and 16, the needle canmlla 1~ is free to
move relative to shoulders 14 and 16 through the
distal bore 12 of syringe cylinder 2.
To this ~nd, FI&. 8 of the drawing~ shows
the needle cannula 18 o~ syringe 1 being withdrawn
through the distal bore 12 to be retracted within and
completely surrounded by the empty medication
cartridge 20. ~ore particularly, the user grasps and
pulls the piston stem 30 proximally through cylinder
2, whereby the needle is relocated from an axially
extended position (shown in phantom and designated by
reference numeral 18-1) to an inwardly retracted
po~ition. When the piston stem (shown in phantom and
designated 30-1) is pulled to the proximal end o
medication cartridge 20, such that the locating bumps
36 are removed therefrom, the retaining fingers 40 o~
the respective gripping arms 34 are automatically
rotated (in the direction o~ the re~erence arrows) out
of engagement with the neck 42 of piston plug member
28. Therefore, the piston stem 30 may be detached
from piston 26 and discarded. However, the piston 26
remains di6posed within the proximal end of cartridge
20, such that the needle 18 is retained at an
inaccessible loration within the interior of the
cartridge. Accordingly, the syringe 1 is now suitable
for disposal with the needle cannula 18 safely
retracted within and completely shielded by both the
medication cartridge 2C and the cylinder 2, whereby to
prevent a reuse of the syringe 1 and its cannula 18
and avoid an accidental needle strike and the spread
~3~ i8
of a communicable and, possibly li~e-threatening,
disease by eliminating the need to handle or cut the
cannula as has heretofore besn required with
con~ntional syringe~
A modi~ication of the d.isposable safety
syringe of FIGs. 1-8 is ~hown in FIG6. 9-14 o~ the
drawings. As was previously indicated when referring
to FIG. 3 of the drawings, a double-ended needle
cannula is firmly bonded to the distal bore of a
syringe cylinder between a pair of needle retaining
shoulders. In the modifiGation of FIGs. 9-14, a
double-ended needle cannula is frictionally engaged
and releasably retained at the distal end of a syringe
cylinder by means of a pair of movable needle
retaining jaws.
More particularly, and referring initially
to FIGs. 9~11, a disposable safety syringe (su~h as a
dental syringe) 50 is shown including a hollow
cylinder 52 haYing open proximal and distal ends.
Extending upwardly from and then across the open
distal end of syringe cylinder 52 is a needle
supporting bridge 54 that is pre~erably formed from a
resilient material. Bridge 54 has an aperture 56
~ormed through a cross member 55 thereof by which to
receive and support a double ended hypodermic needle
¢annula 58 in coaxial alignment with the cylinder 52.
The needle cannula 58 is engaged and
retained at the distal end of the cylinder 52 by a
pair of oppositely disposed needle retaining jaws 60
and 61. Needle retaining jaws 60 and 61 project
radially inward and towards one another from
respective sides of the needle supporting bridge 54.
Retaining jaws 60 and 61 are narrowly spaced from one
another along the longitudinal axis of the syringe
cylinder 52. Therefore, a needle cannula 58 can be
located in the narrow space between the opposing
retaining jaws 60 and 61 and retained therein by means
136~
-14-
of friction so as to prevent the inadvertent
detachment of and/or axial relocation of cannula 58
relative to jaws 60 and 61~ To thls end, the cannula
58 ~ay be provided with an irregularly textured
surface ~2 (best shown in FIG. lO~, ~hereby to enhance
the frictional engagement of cannula 58 by rstaining
jaws 60 and 61.
Each needle retaining jaw l60 and 61 is
connected to a respective side of ne,edle supporting
bridge 54 by an integral hinge 640 As will soon k)e
explained, the application of an axial and distally
directed force to needle retaining jaws 60 and 61 to
cause said jaws to rotate around hinges 64 for
movement out of engagement with needle cannula 58.
Each retaining jaw 60 and 61 also includes a flat
contact face 66. In the configuration of FIGs. 9-11,
the contact faces 66 of jaws 60 and 61 are arranged in
spaced, parallel alignment with one another for
retaining the needle cannula 58 therebetween by means
of the afore~entioned frictional engagement thereof.
A surface portion 68 of each needle
retaining jaw ~0 and 61 below the flat contact face 66
i~ beveled. Such beveled surfaces 68 permit the
retaining jaws 60 and 61 to rotate around thPir
respective hinges 64 in response to a distally
directed force (as will soon be described). That is
to say, without the pre~ence of beveled surfaces 68,
the retaining jaws 60 and 61 would be unable to
rotate, as a consequence of their proximity to the
longitudinally extending needle cannula 58. ~o this
end, and as will be described in greater detail when
referring hereinafter to FIGs. 12 and 13, a
longitudinal channel 69 is formed in each beveled
surface 68 so as to receive the cannula 58 during the
rotation of retaining jaws 60 and 61.
Similar to the syringe of FIGs. 1-8, a pre-
filled medication cartridge or ampule 70 is loaded
6~8
into the syringe cylinder ~2 through the open proximal
end thereof, so that the contents of the cartridge 70
may be injected into a target~d tissue area of a
patient via needle cannula 58. Cartridge 70 lncludes
a metal end cap 72 which ~ecures a rubber seal 74
across the distal end of the cartridge. A neck 76 o~
relatively reduced diameter is formecl around the
periphery of the cartridge 70 below end cap 72. A
piston 26 is located at the proximal end of cartridge
70 and is slideable axially therethrough to expulse
the contents of the cartridge via cannula 58. Piston
26 includes an integrally formed, proximally
projecting plug member 28. Inasmuch as the piston 26
and plug member 28 of the syringe 50 of FIGs. 9-14 are
identical to the piston and plug member of the syringe
of FIGsO 1-9 ~ identical reference numerals will be
used and no ~urther description of said piston 26 and
plug member 28 will be provided.
Syringe 50 also includes a combination
needle sheath and piston stem 30. The needle
sheath/piston stem 30 has an elongated body with a
wide and hollow sleeve 32 formed at one end and a pair
of flexible gripping arms 34 projecting from the
opposite end. Inasmuch as the combination needle
sheath/piston ~tem 30 of the syringe 50 of FIGs. 9~14
is identical to the needle sheath/piston stem of the
syringe of FIGs. 1-8, identical reference numerals
will be used, and no further description of said
needle sheath/piston stem 30 will be provided, except
to say that the needle sheathtpiston stem functions as
a needle sheath when the sleeve 3Z thereof surrounds
one end of the cannula 58, or, as a piston stem, when
the pair of gripping arms 34 are releasably connected
to the plug member 28 of piston 26 to form a complete
35 piston assembly ~as is illustrated in FIGs. g and 10).
The operation of the syringe 50 is now
described while referring to FIGs. 9-14 of the
~6~
-16-
drawings. FIG. 9 illustrates the syringe 50 in the
pre-injection mode (similar to the syringe illustrated
in FIG. 3) with medication cartridge 70 spaced axially
fro~ the needle cannula 58. The cartridg~ 70 i~
retained at the axially spaced position relative to
cannula 58 when a proximal locking de!t~nt 78 of
~yringe cylinder 52 is detachably received within the
narrow neck of the cartridge.
FIGr~ 10 shows the syringe 50 in the
injeation mode (similar to the syringe illustrated in
FIG. 5) after medication cartridge 70 has been
detached from the proximal locking detent 78 and moved
axially through syringe cylinder 52 and the piston
plug member 26 has been engaged by piston stam 30 and
moved distally through the cartridge, so that the
needle cannula 58 penetrates the rubber seal 74 of
cartridge 70 and the contents o~ said cartridge are
expulsed via cannula 58 for the purpose o~
administering an injection. The cartridge 70 is
retained in communication with needle cannula 58 when
a distal locking detent 79 of cylinder 52 is
detachably received within the narrow neck 76 of the
cartridge.
Once the medication cartrid~e 70 of syringe
50 has been emptied and the injection completed, the
health care worker applies an àxial force to the
piston stem 30 ~in the direction of the reference
arrow 80 of FIG. 12~. Accordingly, and re~errinsr now
to FIGs. 12 and 13 of the drawings, the axial force is
transferred from piston stem 30 to the empty
medication cartridge 70 via piston plug member 26,
whereby to move cartridge 70 out of engagement by the
distal locking detent 79 and into contact with the
needla retaining jaws S0 and 61. The axially applied
. 35 for~e is then transferred from the cartridge 70 to
retaining jaws 60 and 61 to cause said jaws to rotate
at the respective integral hinges 64 in a direction
~L3Q~
-17~
away from needle cannula 58. By virtue oP it
resilient nature, the sides of needle supporting
bridge 54 are permitted to bow outwardly to
accommodate the ro~ation o~ ~aws 6~ and 61 against
aannula 58. Accordingly, the needle cannula 58 will
be released from its former ~riction,al engagement by
and betwean the opposing ~lat contact faces 66 of
needle retaining jaws 60 and 61.
The retaining jaws 60 and 61 will continue
to rotate in response to an axia~ force applied
thereto by the distally advancing medication cartridge
70 until the beveled sur*aces 68 thereof are arranged
in face-to face alignment with one another. As i.s
best shown in FIG. 13, the needle cannula 58 is
received within the respective longitudinal channels
69 which are formed in the opposing beveled sur~aces
68. Therefo~e, the cannula 58, which is now retained
at only one end thereof (i.e., from the piston 26)
floats freely within the adjacent channels 69 of the
beveled surfaces 68 and the aperture 56 formed in the
cross member of the needle supporting bridge ~4.
: Referring now to FIG. 14, the freely
floating needle cannula 58 of syringe 50 is withdrawn
(in the direction of the reference arrow 82) through
the aperature 56 in bridge 54 and the adjacent
channels 69 of needle retaining jaws 60 and 61 so as
to be retracted within and completely surrounded by
the empty medication cartridge 70. Inasmuch as the
procedure for withdrawing the cannula 58 into the
cartridge 70 of syringe 50 is identical to the
procedure disclosed when referring to the syringe of
FIG. 8, no further description of this procedure will
be provided, except to say that the health care worker
pulls the piston stem (designated 30 in FIG. 12)
proximally through medication cartridge 70, whereby
the cannula 58, which is attached to the piston 26, is
relocated from an axially extended position (as
6~
-18-
illustrated in the injection mode of FIG. 10) to a
retracted position (as illustrated in the needle
retraction ~ode o~ FIG. 14~o
Because o~ non uni~orm deformation ~txessee
within the piston and axial deflections pxoduced by
needle retaining jaws S0 and 61, the needl~ cannula 58
is retracted into the cartridge 70 in a canted
alignment relative to the longitudinal axis of the
cylinder 52. Therefore, the needle cannula 58 will be
blocked ~e.g. by the end cap of the cartridge) during
any attempt to return the cannula ax:ially and distally
through the cartridge to the axially extended position
of FIG. 10.
As was also previously described when
re~erring to FIG. 8, the piston stem may now be
detached from piston 26 and discarded. However, the
piston 26 remains at a proximal position within
medication cartridge 70, such that the cannula 5~ is
inaccessably located at the interior of the cartridge.
EIence, the ~ringe 50 is now suitable ~or disposal
with the needle cannula safely retracted within and
completely shielded by both the medication cartridge
70 and the syringe cylinder 52, whereby to prevent a
reuse of the syringe and its cannula and thereby avoid
an accidental needle strike and the spread of a
contagious, and possibly life threatening, disease.
It will be apparent that while a preferred
embodiment has been shown and described, various
modifications and changes may be made without
departing from the true spirit and scope of the
inventionO For examplP, the syringes 1 and 50 of the
present invention has been described as having
application as a dental syringe. Nevertheless, this
should not be regarded as a limitation of the scope of
the invention, and the claims which are appended
her~to are applicable to other syringes, especially
those which use a pre-filled medication cartridge,
~3~ 5~
--19 ~
where it is desirable to retract the needle cannula
within the cartridge in order to rencler the syringe
safe ~or handling.
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