Abstrict A non-reusable disposable syringe utilizing a conventional syringe
body, a locking device allowing one full retraction of the plunger
and one full expulsion of the contents wherein the locking device
cooperates with the plunger shaft in advancing the piston in the
expulsion stroke.
Claims I claim:
1. A non-reusable disposable syringe comprising:
(a) a syringe body having an open end and defining an inside surface;
(b) a plunger adapted to be positioned within said syringe body
and to extend from said syringe body, said plunger comprising a
plunger shaft and a plunger head at the end of said shaft adapted
to be positioned in said syringe body, the shaft end on the other
end of said shaft defining spaces for accepting a holding member
to be positioned in said syringe body together with said plunger;
(c) a cylindrical piston dimensioned and configured such that said
piston bears sealingly against the inside, surface of said syringe
body said piston being adapted to be positioned within said syringe
body, said piston defining a central passage, a portion of said
central passage being smaller than said plunger head, and said central
passage being configured and dimensioned to sealingly engage and
be closed by said plunger head, said piston being positioned within
said syringe body with said plunger passing into said central passage,
said piston being adapted to receive said holding member and be
urged by said holding member against said plunger head; and
(d) a locking device supported for slidable movement with respect
to said plunger, said locking device being capable of movement with
respect to said plunger in one direction only and capable of movement
with respect to said syringe body in only one direction, said locking
device being configured and dimensioned to advance said piston with
said plunger after said piston is brought into contact with said
locking device.
2. A syringe as in claim 1 wherein said spaces are holes defined
in an end member disposed on the other end of said shaft.
3. A syringe as in claim 2 wherein said shaft has an irregular
surface.
4. A syringe as in claim 1 wherein said shaft has an irregular
surface.
5. A non-reusable disposable syringe comprising:
(a) a syringe body having an open end and defining an inside surface;
(b) a plunger comprising a ridged plunger shaft, said shaft being
longer than said syringe body, a plunger head and a shaft end defining
a plurality of holes;
(c) a cylindrical piston dimensioned and configured such that said
piston bears sealingly against the inside surface of said syringe
body said piston being positioned within said syringe body, said
piston defining a central passage, a portion of said central passage
being smaller than said plunger head, and said central passage being
configured and dimensioned to sealingly engage and be closed by
said plunger head, said piston being positioned within said syringe
body with said plunger passing into said central passage; and
(d) a locking device supported for slidable movement with respect
to said plunger, said locking device being capable of movement with
respect to said plunger in one direction only and capable of movement
with respect to said syringe body in only one direction, said locking
device being configured and dimensioned to advance said piston with
said plunger after said piston is brought into contact with said
locking device.
6. A non-reusable disposable syringe as claimed in claim 5 wherein
said locking device comprises
(a) a base, proportioned to fit within said syringe body, said
base defining a central opening sufficiently large such that said
plunger shaft may pass through said opening;
(b) a plurality of syringe prongs integrally associated with said
base, extending from said base in an axial direction and radially
outwardly to an extent that at least one cf said syringe prongs
contact said syringe body when said locking device is positioned
in said syringe body; and
(c) a plurality of shaft prongs integrally associated with said
annular base, extending from said base in the same axial direction
as said syringe prongs and also extending radially inwardly to an
extent that at least one of said shaft prongs will contact said
plunger shaft when said plunger shaft is within said central opening.
7. A non-reusable disposable syringe as in claimed in claim 5
wherein said plunger shaft defines a break-away construction.
8. A non-reusable disposable syringe as in claimed in claim 6
wherein said axial direction extends toward the open end of said
syringe body.
9. A non-reusable disposable syringe as claimed in claim 8 wherein
said plunger head initially substantially abuts a closed end of
said syringe body opposite said open end, and wherein said locking
device is positioned adjacent and outside said open end.
10. A non-reusable disposable syringe as claimed in claim 7 wherein
said break-away construction comprises slots cut into said plunger
shaft.
11. A non-reusable disposable syringe as claimed in claim 5 wherein
said locking device comprises four syringe prongs and four shaft
prongs.
12. A non-reusable disposable syringe a claimed in claim 5 wherein
said syringe prongs have sharp pointed tips.
13. A non-reusable disposable syringe as claimed in claim 5 wherein
said plurality of holes are configured, dimensioned and positioned
to permit rods to pass through said shaft end and contact said piston
for the purpose of siliconization.
14. A non-reusable disposable syringe as claimed in claim 5 wherein
said plunger and said locking device are formed of hard plastic
as a single unit.
15. A non-reusable disposable syringe as claimed in claim 14 wherein
said plurality of holes comprise at least two holes configured,
dimensioned and positioned to permit rods to pass through said shaft
end and contact said piston for the purpose of securing said piston
for siliconization and at least one additional hole to allow insertion
of a rod to apply pressure to said locking device and cause said
plunger and said locking device to separate into two separate units.
16. A non-reusable disposable syringe as claimed in claim 5 wherein
said ridged plunger shaft is ridged only over the portion of said
shaft that enters said syringe body when said shaft is advanced
into said syringe body.
17. A non-reusable disposable syringe as claimed in claim 16 wherein
the ridged portion of said ridged plunger shaft is wider than the
unridged portion.
18. A non-reusable disposable syringe as claimed in claim 3 wherein
said irregular plunger shaft is ridged only over the portion of
said shaft that enters said syringe body when said shaft is advanced
into said syringe body.
19. A non-reusable disposable syringe as claimed in claim 3 wherein
said irregular portion of said ridged plunger shaft is wider than
the regular portion.
Description BACKGROUND
The increasing awareness of the importance of sterility in hypodermic
devices, coupled with the continually increasing number of hypodermic
injections given, has led to the advent of disposable syringes.
The initial sterility and low cost of disposable syringes has led
to the widespread use of these syringes and the preference for disposable
syringes over the older reusable glass syringes that require sterilization
before each use.
The disposable syringe, by its very nature, has spawned problems.
The disposable syringe is cheap and disposable and controls on the
inventory of a cheap and plentiful item tend to loosen while controls
on discarded items have generally been lax. It is not uncommon for
syringes, along with the attached needles, to find their way into
unauthorized hands. The syringes may be reused without sterilization
and thereby contribute to a problem they originally were designed
to prevent, i.e. the spread of disease due to contamination.
An unfortunately common unauthorized use of syringes is associated
with the use of illegal drugs. The common practice of sharing the
syringe among drug users dramatically increases the risk of exposure
to, and spread of, disease.
Hepatitis has long been associated with illegal drug use as it
is spread among users of injectable drugs via contaminated hypodermic
devices. Today it is known that the Human Immune Virus associated
with AIDS is spread similarly. Indeed, the highest rate of infection
of AIDS is now found in intravenous drug users and the infection
rate is increasing.
Non-reusable syringes will not stop drug use but can prevent sharing
of contaminated needles and thus help fight the spread of diseases
such as AIDS.
Non-reusable syringes have been designed in the past; however,
there are numerous shortcomings in these earlier versions. Non-retractable
drive shaft or piston arrangements such as found in Butterfield,
U.S. Pat. No. 4493703 require pre-filled syringes as the syringe
may not be filled by the user in the conventional manner. Lip-and-catch
mechanisms of many sorts have been proposed, however until the lip-and-catch
engages, the drive shaft and piston may retract and reuse is possible.
Hesse, U.S. Pat. No. 4731068 requires a catch to be fixedly mounted
and engage a slidable sheath thus requiring additional parts within
the syringe, other embodiments require a plurality of cooperating
parts that add to the complexity, assembly and cost of the syringe.
Owing to the problems or costs of the previous non-reusable syringes
there has been no widespread acceptance and use of these devices
in the medical community.
SUMMARY OF THE INVENTION
The invention is intended to provide a remedy, retaining the advantages
of sterility and low cost of the disposable syringe and incorporating
a locking device preventing reuse. The device cooperates with the
plunger, the piston and the syringe allowing filling, discharging
and aspiration while preventing reuse and some forms of partial
use or misuse.
BRIEF DESCRIPTION OF THE DRAWINGS
One way of carrying out the invention is described in detail below
with reference t drawings which illustrate only exemplary specific
embodiments of the invention and in which:
FIG. 1 is a view of the inventive syringe in the initial empty
condition;
FIG. 2 is a cross-section of the syringe in FIG. 1 during the filling
movement;
FIG. 3 is a cross-section of the syringe in FIG. 1 showing the
result of an attempted premature discharge;
FIG. 4 is a cross-section of the syringe in FIG. 1 showing the
plunger fully retracted;
FIG. 5 is a cross-section of the syringe in FIG. 1 during the discharge
motion;
FIG. 6 is a cross-section of the syringe in FIG. 1 after complete
discharge;
FIG. 7 is a cross-section of a second embodiment of the inventive
syringe during the discharge motion;
FIG. 8 is a cross-section of the syringe in FIG. 7 during aspiration;
FIG. 9 is a cross-section of a locking device compatible with the
syringe of FIGS. 1 through 6;
FIG. 10 is a top view of a locking device;
FIG. 11 is a cross-section of a locking device compatible with
the syringe of FIGS. 7 and 8;
FIG. 12 illustrates a locking device in plan;
FIG. 13 is a view along lines 13--13 of FIG. 12;
FIG. 14 is a view of an alternate embodiment plunger, piston and
locking device group in a sectioned syringe body; and
FIG. 15 is a plan view of the external shell end of the embodiment
shown in FIG. 14.
BEST MODE FOR CARRYING OUT THE INVENTION
Referring to FIG. 1 the structure of the inventive syringe 10
is seen to comprise a plastic plunger shaft 12 integral with the
plunger head 14 which is larger in diameter than the shaft, the
shaft defining slots 16 and 18 to cause a weak area in the shaft
forming a frangible portion. Shaft 12 is formed with a cross-section
of a cross. A rubber piston 20 bears sealingly against the inner
syringe wall 28 of a conventional syringe body 30. The plunger head
fits within and sealingly conforms to a piston recess 22 best illustrated
in FIGS. 2 and 3 the rear lip 24 of plunger head 14 bearing against
the recess seat 26. A shaft stabilizer 13 is secured at the end
of syringe body 30 to keep the shaft 12 from becoming decentered
in body 30.
A spring locking device 32 is positioned at the rear of the syringe
body in the initial, empty condition as illustrated in FIG. 1. In
this position, the plunger head 14 is in the forward portion of
the syringe body 30. When it is desired to use the inventive syringe,
shaft 12 is pulled backwards, to draw the medicinal fluid into the
syringe. FIG. 2 illustrates the plunger moving backwards. Plunger
head 14 is pulled tight against recess seat 26 forming a seal and
therefore reducing the pressure in the syringe interior 34 during
backwards motion in the direction indicated by arrow 35 drawing
a fluid into the syringe interior through a needle orifice 36 within
a needle support 37. Plunger shaft 12 moves backwards easily over
back-facing shaft prongs 38 and 40 of the locking device because
they are oriented in the same direction as relative movement of
shaft 12 while back-facing syringe prongs 42 and 44 prevent backward
motion of the locking device 32 with respect to the syringe by digging
into the inner syringe wall because they are pointed against the
direction of relative movement of inner syringe wall 28. These prongs
may terminate in a point to enhance their bite into the inner wall.
Forward motion of the plunger before complete retraction causes
the plunger head to leave its position against recess seat 26 breaking
the seal and leaving piston 20 in its position as illustrated in
FIG. 3 causing leakage of the contents. FIG. 3 shows the positions
of the locking device and the piston based upon forward motion of
the shaft from the respective positions illustrated in FIG. 2.
After the completion of retraction, piston 20 is firmly secured
between locking device 32 and plunger head 14. The forward motion
of shaft 12 causes shaft 12 to engage shaft prongs 38 and 40. These
prongs may also have pointed ends. FIG. 4 depicts the inventive
syringe with shaft 12 fully retracted. Plunger head 14 is sealingly
engaged against recess seat 26 and piston 20 is in forced contact
with locking device 32. Engagement of prongs 38 and 40 during forward
motion moves locking device 32 forward with the shaft as syringe
prongs 42 and 44 allow forward motion of the locking device with
respect to the syringe because they do not engage the wall 28 due
to a reversal of the relative motion involved. Since the prior rearward
motion of shaft 12 has brought the locking device into contact with
the piston, as illustrated in FIG. 4 during forward motion the
forward surface of the locking device move the piston forward with
the shaft.
As the plunger shaft is moved forward to discharge the medicine
into the patient, prongs 38 and 40 hold the locking device in forced
contact with piston 20 and plunger head 14 remains sealingly engaged
against recess seat 26. The plunger shaft and head, the locking
device and the piston move as a unit pressuring the contents of
syringe interior 34 to move through needle orifice 36. As illustrated
in FIG. 5 the locking device is moved forward by the shaft as shaft
prongs 38 and 40 will not allow forward motion of the shaft with
respect to the locking device. It is locking device 32 that drives
piston 20 forward as the shaft is moved forward. Locking device
32 is, in turn, driven by shaft 12.
FIG. 6 shows the syringe completely discharged. Syringe prongs
42 and 44 prevent backward motion of the locking device and therefore
also prevent the backward motion of the shaft and the piston. No
further function is possible Slots 16 and 18 forming the break-away
construction, permit the shaft to break before the locking device
moves in the situation where excess force is used in an attempt
to retract the piston a second time.
An alternative embodiment incorporates a piston which allows aspiration.
In this embodiment, as illustrated in FIG. 7 shaft prongs 138 and
140 are modified so that no biting or digging engagement may take
place with respect to plunger shaft 112. Engagement of prongs 138
and 140 with plunger shaft 112 occurs by means of catches 150 and
152 positioned on shaft 112. When prongs 138 and 140 engage catches
150 and 152 respectively, the locking device 132 abuts piston 120
in the same manner as locking device 32 abuts piston 20 in FIGS.
4 5 and 6 allowing the discharge of the fluid in the syringe interior
134. Generally, after filling, a small amount of medicine will be
discharged together with any air bubbles to put the syringe in the
position illustrated in FIG. 7.
In this embodiment, piston 120 is longer than the piston of the
first embodiment and has an external annular indent 154 and an internal
annular hollow 156. The piston material between annular indent 154
and annular hollow 156 is sufficiently solid to hold the plunger
head sealingly engaged to the piston when the assembly is advancing,
the piston being pushed along by the locking device engaged on catches
150 and 152. The annular indent and the annular hollow do, however,
sufficiently increase the deformability of the piston at this point
to allow a flexing if the plunger head provides a backward force
on the piston, as illustrated in FIG. 8. During aspiration, a backward
force is applied by retracting the plunger shaft. Aspiration is
a means of determining whether or not the needle is in a blood vessel.
Backward motion of the shaft, to the extent allowed by the piston
flexing between indent 154 and hollow 156 is allowed by prongs
138 and 140 while prongs 142 and 144 hold the locking device stationary
with respect to the syringe. Such backward motion will result in
visibly drawing blood into the syringe if the needle is in a blood
vessel.
Forward movement as a result of the release of the previously applied
pressure on shaft 112 follows aspiration and allows the piston to
return to the unflexed position as prongs 138 and 140 allow the
shaft to move forward with respect to the locking device until catches
150 and 152 are reencountered In this manner, aspiration may be
achieved without affecting the single-use quality of the syringe
or the basic mechanism employed to achieve the single-use aspect
of the inventive syringe.
The locking device may consist of a ring 80 or other shape allowing
the plunger shaft to pass through its center with resilient wire
prongs attached to the ring, as illustrated in FIGS. 9 and 10. Alignment
members 82 may also be incorporated. flattened or planar members
may be used instead of wire. The ring may be constructed of metal
or plastic, the prongs are preferably formed from metal. The wire
used may be spring steel and may be welded or soldered to a metal
ring or may be stamped integrally therewith The prongs may be pointed
to enhance their "biting" ability.
However, in the case of the embodiment shown in FIGS. 7 and 8
sharpening of the inner-directing, shaft prongs such as 138 and
140 is to be avoided (FIG. 11). Additionally, the prongs are to
be shaped to avoid digging into the cylindrical shaft but capable
of engaging the catches positioned on the shaft.
A self-aligning stamped star-washer type of locking member 232
is illustrated in FIG. 12. Here the shaft 212 shaped as a cross
in cross-section has inner rounded surfaces 284 which engage inner
gripping members 286 mounted on ring 288 which is integral with
outer gripping member 290. As can be seen from FIG. 13 locking
member 232 can be stamped from reliant sheet metal.
The slots forming the frangible portion of the shaft may be placed
behind the point where the locking device prongs engage the shaft
so that the break-away construction may serve to prevent forced
twisting of the shaft to loosen the bite that the locking device
may have on the cylinder or shaft, as illustrated in phantom lines
in FIG. 7 and 8. In this manner, the shaft will separate into two
parts before the twisting motion is significantly transferred to
the locking device which may adversely affect the device's function.
The syringe and the plunger shaft are constructed of the normal
materials associated with disposable syringes now in use, i.e. plastics
or polymers and copolymers such as polyethylene, polypropylene,
polystyrene, polybutylstyrene, etc.
FIG. 14 shows a plunger shaft 312 that is longer than the syringe
body, has texturing or ridging 302 along most of the shaft's length
and a modified external shaft end 303.
Plunger shaft 312 is long enough to allow piston 320 to be fully
inserted into the syringe while not causing locking device 332 to
engage the syringe body. This allows for siliconization of the syringe
body and seal by the moving of the plunger through the body a requisite
number of times before use. Rods 305 are inserted in holes 304 to
push piston 320 forward without the contact of .locking device 332.
The use of two rods 305 in holes 304 of FIG. 15 provide adequate
and balanced pushing to advance piston 320.
In this embodiment, both shaft 312 and locking device 332 may be
molded out of hard plastic and molded as a single unit. The locking
device and shaft may be joined during molding at points 339 where
shaft prongs 338 meet shaft 312. Inserting straight rods 307 (illustrated
in phantom lines) through holes 306 to contact locking device 332
and then applying pressure will break the locking device 332 and
shaft 312 apart at points 339. Ridging or texturing 302 will insure
a locking relationship between locking device 332 and shaft 312
even if shaft prong 338 is not particularly sharp due to uneven
breaking of the one piece molded subassembly.
After lubrication, holes 306 are used to advance the locking device
into the syringe body to the position illustrated in FIG. 1. This
approach can be used equally in the case of a one-piece plastic
locking device-shaft unit or a separate plastic or metal locking
device Rods 307 pass through holes 306 to engage the locking device
and make the syringe non-reusable. Locking device 332 may be advanced
to any desired position within the syringe to limit the syringe
capacity to draw in fluid and therefore prevent waste.
Contact between plunger head 314 and piston 320 at surface 325
should be angled to generate perpendicular compression forces in
order to comply with FDA pressure requirements.
Ridging 302 makes the shaft wider over the portion of the shaft
that fits within the syringe body. The purpose of the ridging may
be accomplished by merely making this section of the plunger shaft
wider than the portion that does not enter into the syringe body.
The extra width will cause more pressure between the shaft prongs
and the shaft.
While an illustrative embodiment of the invention has been described
above, it is, of course, understood that various modifications will
be apparent to those of ordinary skill in the art. Such modifications
are within the spirit and scope of the invention, which is limited
and defined only by the appended claims. |