The disposable syringe comprises a cylindrical barrel having a
side wall, an axis, and two ends, one of which, the distal end,
has an inlet-outlet end for the administration of fluids. A cylindrical
plunger is mounted snugly and fluid tight for axial movement within
the barrel. An actuating rod has one, distal end connected to the
plunger. The barrel at its other, proximal end has means for guiding
the actuating rod axially. One or more pins of spring material are
within the barrel, one, proximal end imbedded in the barrel side
wall, and the other, free distal end located nearer the distal end
of the barrel then the location of the proximal end of the pin.
The plunger is movable from a position nearer the proximal barrel
end to a position nearer the other, distal barrel end beyond the
distal end of the pin, the barrel head on such movement camming
the pin head outward from its normal position toward the wall of
the barrel until the free end is freed by elasticity of the pin
to return to its normal position radially within the wall, whereby
on such movement the head is captured by the interposed pin free
end to prevent return movement of the head toward the proximal end
of the barrel thereby to prevent re-use of the syringe.
1. A disposable syringe for one-time use comprising:
a cylindrical barrel having a side wall, an axis, and two ends
one of which is a distal end for the administration of a fluid;
a cylindrical plunger mounted snugly and fluid tight for axial
movement within the barrel;
an actuating rod connected to the plunger and of radial extent
less than that of the plunger, the barrel having at the other, proximal
end means for guiding the actuating rod axially;
a pin of spring material within the barrel and having two ends,
the proximal end being securely fixed and sealed imbedded in the
side wall at an axial position and the other, distal end being free
and located axially within the barrel nearer the other, distal end
of the barrel than the axial position of imbedment of the pin and
having a position radially within the side wall;
the plunger being movable by the actuating rod from a position
nearer the one, distal barrel end to a position nearer the other,
proximal barrel end and beyond the proximal end of the pin, the
barrel on such movement camming the pin free end aside from its
normal position toward the wall of the barrel until with continued
plunger movement the free end is freed and returns by elasticity
of the spring material to its normal position radially within the
whereby on such movement the plunger is captured by the pin at
its free end to prevent return movement of the plunger toward the
proximal end of the barrel and thereby to prevent re-use of the
2. A disposable syringe as claimed in claim 1 further comprising
at least one other pin of spring material located within the barrel
and each said pin having two ends, one, proximal end being securely
fixed and sealed to the side wall at the same axial position as
the first pin but at equal angular intervals about the axis, and
the other, distal ends of the other pins being free and located
axially at the same point as the distal end of the first pin.
3. A disposable syringe as claimed in claim 1 the said side wall
possessing a buttressing support of greater diameter than the cylindrical
portion to lend support for the said pin at the proximal position
of the pin.
4. A disposable syringe as claimed in claim 1 the said syringe
having a stroke in the axial direction toward the barrel distal
end closer to the barrel distal end than the distal pin end.
5. A disposable syringe as claimed in claim 1 the said syringe
having a stroke in the axial direction toward the distal barrel
end beyond the position of the distal end of the pin.
6. A disposable syringe as claimed in claim 1 the pin having a
head at the free, distal end facing the barrel, and the barrel having
a pocket to receive the pin head during the camming action of the
7. A disposable syringe as claimed in claim 5 further comprising
a compression spring contained within the pocket to assist the pin
in moving towards its normal position radially within the side wall.
8. A disposable syringe as claimed in claim 2 further comprising
a ring about the side wall at the position of the seal and itself
sealed to the side wall to lend support to the said pins at the
9. A disposable syringe as claimed in claim 1 the said pin being
circular in cross-sectional shape.
10. A disposable syringe as claimed in claim 1 the said pin being
rectangular in cross-sectional shape.
11. A disposable syringe as claimed in claim 1 the said guiding
means comprising a head for the barrel having an opening, the said
actuating rod having a cross-sectional shape complementary to said
opening and closely fitting within it.
12. A disposable syringe as claimed in claim 11 the said guiding
means opening being circular.
13. A disposable syringe as claimed in claim 11 the said guiding
opening being non-circular.
14. A disposable syringe as claimed in claim 11 the said guiding
means being tripartite, with three similar parts about the axis.
15. A disposable syringe as claimed in claim 11 the said guiding
means being quadripartite, with four similar parts symmetrical about
16. A disposable syringe as claimed in claim 11 the said guiding
means having axial extent and elasticity, the actuating rod camming
the guiding means open as the rod moves toward the distal end, the
actuating rod having a portion smaller in diametral extent about
the axis at the distal end, whereby the guiding means, after a full
stroke of the actuating rod and plunger, interferes by interposition
to prevent a return stroke of the rod.
17. A disposable syringe as claimed in claim 1 the said barrel
having an open groove to receive the pin throughout its length except
for the imbedded end, whereby the length of the pin is smooth within
the barrel as the plunger passes over the pin.
18. A syringe as claimed in claim 2 there being one other pin
located diametrically opposite the first pin.
FIELD OF THE INVENTION
The invention relates to disposable syringes which are intended
for one-time use.
BACKGROUND OF THE INVENTION
Many efforts have been made to provide disposable syringes intended
for one-time use. For example: U.S. Pat. No. 3478937 to Solowey
Nov. 18 1969 for Disposable Single Unit-dose Syringe with Locking
Plunger has pawls 41 pivoted into notches 44 by force of the edge
of the rigid collar 46 and after passing through the collar, the
pawls spring outward to prevent upward movement of the plunger.
U.S. Pat. No. 3890971 to Leeson et al. June 24 1975 for Safety
Syringe describes a detent 19 having an upwardly inclined groove
locking face 18b in order to prevent downward movement of the plunger
after initial use.
U.S. Pat. No. 4233975 to Yerman Nov. 18 1980 for Anti-drug Abuse
Single-use Syringe describes a terminal end blocking flow through
outlet 17 when female members 25 flexibly and resiliently snap back
into locking position blocking flow into or from needle 22.
U.S. Pat. No. 4252118 to Richard et al. for Nonreusable Drug
Prefilled Syringe Assembly and Method of Use describes a stopper
and rod which become disconnected from each other after an injection
is given and the plunger rod is withdrawn inside the barrel.
U.S. patent to Legendre et al. Jan. 11 1983 for Pre-filled Syringe
for Abusable Drugs describes a spike 14 on a plunger rod 13 which
prevent the rod from being withdrawn backward through the restricted
U.S. Pat. No. 4391272 to Staempfli July 5 1983 for Disposable
Syringe describes a rim 7 of a plunger 6 which is blocked against
the body 11 of the groove 5 which prevents the rearward return movement
of the piston body 3.
U.S. Pat. No. 4391273 to Chiquiar-Arias July 5 1983 for Non-reusable
Disposable Syringes describes a sharp point of pin 67 which penetrates
the bottom wall of the cylinder when the plunger is pressed home,
making the syringe useless thereafter.
U.S. Pat. No. 4493703 to Butterfield Jan. 15 1985 for Hypodermic
Syringe Cartridge with Non-retractable Drive Piston which describes
an actuator rod which disengages from an insert 18 when the rod
is pulled away from the piston.
U.S. Pat. No. 4650468 to Jennings, Jr. Mar. 17 1987 for Retractable
Disposable Syringe describes various locking arrangements in which
the cannula is withdrawn into the cylindrical body and securely
locked within it.
SUMMARY OF THE INVENTION
According to the invention the disposable syringe for one-time
use comprises a cylindrical barrel having an inlet-outlet end, a
cylindrical plunger mounted fluid tight for axial movement in the
barrel, an actuating rod for the plunger and having one end connected
to the plunger, and the barrel having at the other barrel end means
for guiding the rod axially. A pin within the barrel has two ends,
one end fixed to the side wall of the barrel, and the other end
free. When the plunger is moved toward the one end it cams the pin
and its free end aside, and after it passes the pin, the pin returns
to normal position and captures the plunger by interposing its free
end to prevent return movement of the plunger. Thus the re-use of
the syringe is prevented. The invention also involves a variety
of other novel features.
DESCRIPTION OF THE DRAWING
The various objects, advantages, and novel features of the invention
will be more fully apparent from the following detailed description
when read in connection with the accompanying drawing, in which
like reference characters refer to like parts, and in which:
FIG. 1 is a schematic view of an embodiment of the invention;
FIG. 2 is a schematic view of the embodiment of FIG. 1 with the
plunger in retracted position;
FIG. 3 is a schematic view of FIG. 1 with the plunger in fully
FIG. 4 is a partial schematic view of another embodiment of the
invention with the plunger in retracted position;
FIG. 5 is a partial schematic view of another embodiment of the
invention with the plunger in a fully extended position;
FIG. 6 is a partial schematic view of still another embodiment
of the invention;
FIG. 7 is a partial schematic view of still another embodiment
of the invention;
FIG. 8 is a schematic view of a different embodiment of the invention;
FIG. 9 is a sectional view of the embodiment of FIG. 8 along the
lines 9--9 of FIG. 8;
FIG. 10 is a perspective view of a modified cap of the embodiment
of FIG. 8;
FIG. 10A is a side view of the plunger alone;
FIG. 11 is a view of the embodiment of FIG. 8 with the piston head
in a different position and also showing a variation in construction;
FIG. 12 is a partial view showing an alternative manner in which
pins may be fastened in the barrel of the syringe;
FIG. 13 is a perspective view of a different pin that may be employed
in various embodiments;
FIG. 14 is a perspective view of a different pin that may be employed
in various embodiments; and
FIG. 15 illustrates a means of attaching an actuating rod to a
A syringe 20 has a barrel 21 a plunger 22 which is fitted snugly
and fluid tight within the barrel 21 to move axially along the direction
of the axis 23. One end 25 the distal end, of the actuating rod
24 is connected to the plunger 22 to move the plunger toward one
end 26 the distal end of the barrel 21 or toward the other, proximal
end 27. The plunger 22 has a proximal face 32. The rod is guided
by means of a cap 28 and a guiding aperture 29 in the cap capping
the other, proximal end 27 of the barrel. The rod 24 has its other,
proximal end 30 connected to a hand or finger grip 31.
One or more pins 33 are shown in FIGS. 1-3 all alike and disposed
at equal angular intervals about the axis 23. Description of one
will serve for all. The pin 33 has at one, distal end 34 a bend
or snub 35 having a surface 37 facing axially. The pins 33 are made
of a spring material so that they will yield to radial forces and
spring back. The other, proximal end 36 of the pins 33 are imbedded
in the side wall 38 of the barrel 21. The side wall 38 of the barrel
21 is enlarged circumferentially as at 39 to strengthen the barrel
about the other, proximal end 36 of the pins 33. The proximal end
36 of the pin 33 is imbedded in the side wall 38 and particularly
in the enlarged portion 39. A small cell or pocket 40 is designed
to receive the snub 35 of the free, distal end 34 when the pin 33
is pressed against the wall 38 as shown in FIG. 1.
In the front or forward direction of the syringe 20 the barrel
terminates in a frusto-conical section 41 which is extended to a
smaller angle conical nozzle 42 in the proximal direction designed
to receive the proximal end of a needle (not shown) for administration
of an injection. The nozzle has at least one raised rib 45 which
seats in a rib receiving indent in the cap of a needle for various
sizes of needles not shown. The distal face 43 of the plunger 22
is shaped conically to substantially match complementarily the frustoconical
section 41 so that virtually all of the solution may be expressed
in the administration of an injection.
In operation the syringe 20 is prepared at the factory with the
plunger 22 only slightly withdrawn from the section 41. At this
point the plunger 22 holds the pins 33 against the side wall 38
of the barrel 21. The solution to be administered may now be drawn
into the barrel 21 by withdrawing the plunger using the rod 24 to
position the plunger 22 to a position as shown in FIG. 2. After
the needle (not shown) is fitted to the nozzle 42 and any extra
air or gas expelled, the solution may be administered using grip
31 to force the rod to the distal end of its stroke, as shown in
FIG. 3. As the plunger 22 passes down the barrel 21 from or near
its most proximal position as shown in FIG. 2 towards the distal
end, the plunger cams the pins 33 toward the side wall 38 and eventually
the snubs 35 enter the pockets 40. When the proximal end of the
plunger 22 passes the free, distal ends 34 of the pins 33 the pins
are released axially, and the free distal ends 34 spring back to
their normal position as indicated in FIGS. 2 or 3. If an attempt
is made to withdraw the plunger proximally as best shown in FIG.
3 the free ends 34 and the surface 37 of the snubs 35 are interposed
against the proximal face 32 of the plunger 22 preventing its return
proximally. Therefore the syringe 20 may be used only once, and
is now disposable.
The pins 33 may be employed without the snubs 35. Nevertheless
the snubs 35 are useful in providing a more sure interposition against
the withdrawal of the plunger 22 after use. The pockets 40 afford
a way of storing the snubs 35 out of the way as the pins 33 are
cammed aside by the distal stroke of the plunger 22.
In FIGS. 4 and 5 an arrangement similar to that of FIGS. 1-3 is
illustrated, except that in the arrangement of FIGS. 4 and 5 an
open groove 47 permits the pin 33 to rest therein throughout the
length of the groove, and the pocket 40 is provided at the distal
end of the groove. Nevertheless the imbedding of the pin 33 at its
proximal end 36 may be modified sufficiently to assure that the
free, distal end 34 of the pin 33 is carried well out into the barrel
21 spaced inwardly from the side wall 38 as indicated in FIG. 5.
In FIGS. 6 and 7 the imbedded end 36 of the pin 33 is distally
located at the farthest position proximally that may be reached
by the plunger 22. This arrangement assures that the piston always
holds the pins 33 retained in the grooves 47 until the plunger
makes a full stroke and reaches proximally to free the free, distal
end 34 of the pins 33. Then the pins spring into their free position,
indicated in dotted lines in FIG. 6.
FIG. 7 is similar to the arrangement of FIGS. 4 and 5 except that
a compression spring 49 within the pocket 40 insures positively
a return of the spring 33 to its normal position outside the groove
47 when the plunger 22 passes by the pin 33 proximally. In this
case the snub 35 at the proximal end 36 of the pin 33 may be modified
to assure that the spring 49 will bear upon the snub 35 urging the
snub towards the center of the barrel so that the surface 37 of
the snub 35 will contact the inner face 32 of the plunger after
it has passed by the snub and prevent the plunger from being withdrawn
FIG. 8 illustrates another embodiment in which the side wall 38
of the barrel 21 at the place of imbedding of the proximal end
36 of the pins 33 is thickened, as at 53 to provide an additional
support for the proximal ends 36. The proximal ends 36 may be slightly
modified by including a hook 54. The thickened portion 53 may encircle
the barrel 21 and any process may be used to bind the pins within
the thickened portion 53 and bind the thickened portion 53 to the
barrel 21. A needle 46 has a rib receiving indent 48.
In the embodiment of FIG. 10 the guiding, proximal end cap 28 is
modified to provide a quadri-partite female guide openings 71 72
73 and 74. The female guide openings receive a plunger having elongated
male members 81 82 83 84 which slide through said female guides
into elongated guiding wings 85 86 87 88 which extend axially
within the barrel of cap 28. As the plunger is either retracted
or fully extended, the guides prevent the plunger from being rotated
and the pins broken off thereby preventing reuse of the syringe.
The rod 24 is in this embodiment elongated in a cruciform cross-sectional
shape. (see FIG. 9). The cruciform shape is complementary to the
cruciform opening in the cap 28. The elongated guiding wings 85
86 87 and 88 at their distal ends 91 92 93 and 94 are modified
to provide a quadri-partite guiding form.
The elongated wings 85 86 87 and 88 are narrowed as they approach
the proximal ends 57 near the cap 28. The guiding wings 85 86
87 and 88 are sufficiently narrowed at their proximal ends 57 so
that they may flex. The purpose of this arrangement is to allow
head 59 at the distal end of the rod adjoining and joined to the
plunger 22 to pass by the wings 85 86 87 and 88 and spread the
broader distal ends 91-94 of the guiding wings 85-88. After the
head 59 passes through the guiding wings, the joined plunger and
head 59 may not return beyond the distal end of the guiding wings.
This restricts the volume or dosage which may be administered by
the syringe 20. At the same time with this modification, as with
others, the plunger 22 after passing distally beyond the distal
ends 34 of the pins 33 is prevented from returning toward the proximal
end by the interposition of the distal ends 34 of the pins 33 as
shown in FIG. 11. A tri-partite dimension (not illustrated) may
also be employed, being also non-circular and symmetrical about
FIG. 12 is a partial view which illustrates a different way in
which the pins may be attached to the barrel 21. A ring 60 is slipped
over the barrel and over the portion at which the proximal ends
36 of the pins 33 are to be sealed. Heat treatment of this portion
then causes the sleeve to become sufficiently soft for penetration
of the ends 36 of the pins to be imbedded within the ring 60 and
the wall 38 of the barrel 21.
The particular shape of the pins is not critical. For example the
pin may preferably be of round cross-section, as indicated in the
perspective view of FIG. 12 and 13 or of rectangular cross-section,
as indicated in the perspective view of FIG. 14.
FIG. 15 illustrates a manner of attaching the head 59 to the plunger
22. The head 59 may have a nipple 61 centrally on its distal side
which mates with a matching centrally located aperture 62 on the
inner face 32 of the plunger 22. When the head 59 is pressed against
the plunger face 32 the nipple 61 is forced into the mating aperture
62 and the enlarged plastic nipple head enters the enlargement of
the aperture to attach the head 59 to the plunger 22. With this
arrangement it is not possible to withdraw the head 59 against the
force of the pins 33 because the head 59 will then pull the nipple
61 from its lodgment in the aperture 62 causing the parts to separate.
Clearly a similar arrangement will be operative with any of the
embodiments by supplying a head 59 with the nipple and the plunger
with the mating aperture, or vice versa.
Preferably the syringe is constructed of a resin based material,
for the various parts, except for the pins, which preferably are
of stainless steel. The plunger 22 rod 24 in any of its forms,
and the grip 31 may be of a suitable metal.
From the foregoing description it is apparent that there is described
a syringe for one-time use for the administration of injections.
The invention as described is susceptible to various modifications,
changes, and adaptations, and these are intended to be comprehended
within the meaning and range of equivalents of the appended claims.