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 locking device for use in a plastic disposable syringe body
with an open end, and fitting around a plunger shaft associated
with said syringe body, comprising:
(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 syringe prong integrally associated with said base, extending
from said base in an axial direction and radially outwardly to an
extent that said syringe prong contacts said syringe body when said
locking device is positioned in said syringe body; and
(c) a shaft prong integrally associated with said base, extending
from said base in the same axial direction as said syringe prong
and extending radially inwardly to an extent that said shaft prong
contacts said plunger shaft when said plunger shaft is within said
central opening.
2. A locking device as claimed in claim 1 wherein said locking
device further comprises three additional syringe prongs and three
additional shaft prongs arranged at 90.degree. intervals around
said base, said base being substantially circular in configuration.
3. A locking device as claimed in claim 1 wherein said syringe
prongs have pointed tips.
4. A locking device as claimed in claim 2 wherein said base in
annular and said syringe prongs and said shaft prongs are comprised
of metal.
5. A locking device as claimed in claim 4 wherein said syringe
prongs, said shaft prongs and said base are formed from a single
piece of sheet metal, said shaft prongs being positioned, configured
and dimensioned to engage the juncture between fins of a multifinned
shaft.
6. A looking device as claimed in claim 4 wherein said syringe
prongs and said shaft prongs are welded to said base.
7. A non-reusable disposable syringe comprising:
(a) a syringe body having an open end and defining an inside surface;
(b) a plunger comprising a plunger shaft and a plunger head;
(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, aid
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.
8. A non-reusable disposable syringe as in claim 7 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 of 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.
9. A non-reusable disposable syringe as in claim 7 wherein said
plunger shaft defines a break-away construction.
10. A non-reusable disposable syringe as in claim 8 wherein said
axial direction extends toward the open end of said syringe body.
11. A non-reusable disposable syringe as in claim 10 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 said open end.
12. A non-reusable disposable syringe as in claim 9 wherein said
break-away construction comprises slots cut into said plunger shaft.
13. A non-reusable disposable syringe as in claim 12 wherein sad
slots are placed upon said shaft such that sad locking device may
be positioned between said piston and said slots.
14. A non-reusable disposable syringe as in claim 7 wherein said
shaft comprises catches to engage said shaft prongs and hold said
locking device in forced contact with said piston.
15. A non-reusable disposable syringe as in claim 7 wherein said
syringe further comprises a plunger shaft stabilizer.
16. A non-reusable disposable syringe comprising:
(a) a plastic syringe body comprising an open end, a substantially
closed end forming a needle support and defining a needle orifice,
and an interior surface defining an interior volume;
(b) a plunger comprising a plunger shaft, a plunger head, said
plunger head being of greater diameter than said plunger shaft,
raised catches on said plunger shaft near said plunger head, and
a frangible portion;
(c) a plunger shaft stabilizer positioned at said open end of said
syringe body;
(d) an cylindrical piston dimensioned and configured such that
said piston bears sealingly against said syringe body when inserted
within said syringe body, said piston comprising a central passage
sufficiently large to accommodate said plunger shaft and, at a point
insufficient to accommodate said plunger head and capable of sealingly
engaging said plunger head and positioned with said plunger shaft
passing through said central passage; and
(e) a locking device comprising:
(i) 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;
(ii) 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 of said syringe prongs
contact said syringe body when said locking device is positioned
in said syringe body and allow movement of said base in one direction
only with respect to said syringe body, said direction being towards
said substantially closed end; and
(iii) 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 the
extent that at least one of said shaft prongs will contact said
plunger shaft when said plunger shaft is within said central opening
and will lockingly engage with said raised catches holding said
locking device in forced contact with said piston.
17. A non-reusable disposable syringe as claimed in claim 16 wherein
said locking device comprises four syringe prongs and four shaft
prongs.
18. A non-reusable disposable syringe as claimed in claim 16 wherein
said syringe prongs have sharp pointed tips.
19. A locking device as claimed in claim 16 wherein said annular
base and said syringe prongs and said shaft prongs are comprised
of metal.
20. A non-reusable disposable syringe as claimed in claim 14 wherein
said piston has an annular external indent and a concentric interior
annular hollow resulting in a thin area of said piston between said
indent and said hollow such that said thin area is capable of flexing
when said piston is forced back against said locking device, capable
of returning to an at rest condition when the back force is removed
and capable of retaining the at rest condition when said piston
is forced by only said locking device.
21. A non-reusable disposable syringe as claimed in claim 16 wherein
said piston has an annular external indent and a concentric interior
annular hollow resulting in a thin area of said piston between said
indent and said hollow such that said thin area is capable of flexing
when said piston is forced back against said locking device, capable
of returning to an at rest condition when the back force is removed
and capable of retaining the at rest condition when said piston
is forced by only said locking device.
Description TECHNICAL FIELD
The present invention relates to hypodermic syringes. In particular,
the invention is drawn to a disposable syringe that cannot be reused.
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 the disposable syringes has
led to the widespread use of these syringes and the preference of
the 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 to drawings which illustrate only two specific embodiments
of the invention and in which:
FIG. 1 is a cross section 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; and
FIG. 13 is a view along lines 13--13 of FIG. 12.
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 comprising four fins 19. 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 FIG. 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.
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, drawing a fluid into the syringe interior through
the needle orifice 36 within needle support 37. Plunger shaft 12
moves backwards easily over back-facing shaft prongs 38 and 40 of
the locking device, while back-facing syringe prongs 42 and 44 prevent
backward motion of the locking device with respect to the syringe
by digging into the inner syringe wall. These prongs may terminates
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.
The forward motion of the shaft causes it to engage shaft prongs
38 and 40 these prongs may also have pointed ends and moves the
locking device forward with the shaft as syringe prongs 42 and 44
allow forward motion of the locking device with respect to the syringe.
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 moves the
piston forward with the shaft. 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.
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.
As the plunger shaft is moved forward 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.
FIG. 6 shows the syringe completely discharged. Syringe prong 42
and 44 prevent backward motion of the locking device and therefor
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 incorporate a piston which allows aspiration
with only minor changes to the design. 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 such that
when prongs 138 and 140 engage catches 150 and 152 respectively,
the locking device 132 is abutting 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.
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 weaken 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. The backward force is applied by retracting
the plunge shaft. 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.
Release of backward force on shaft 112 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. Aspiration is a means of determining whether or not the
needle is in a blood vessel.
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. 4). 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. 18 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 ma 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.
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. |