A disposable syringe for use in a needleless hypodermic injector
includes a transparent, plastic barrel with an injection orifice
in a closed front end thereof and an open rear end for receiving
a plunger. The barrel is filled with medicine using a needle, which
may be integral with the barrel, by partially withdrawing the plunger
from the barrel to suck medicine through the injection orifice.
The barrel and plunger are placed in an injector and the injector
is actuated to push the plunger into the barrel, discharging the
medicine. Alternatively, the syringe is filled with medicine while
in an injector of the type which includes a removable injection
head and a removable charging or filling head.
1. A disposable syringe for use in a needleless injector of the
type including a casing, a piston slidably mounted in the casing
for movement between a retracted position and an extended position,
and drive means for driving the piston from the retracted to the
extended position, the syringe comprising tubular plastic barrel
means, said barrel means having an open inner end for insertion
into said casing and a closed outer end for extending out of said
casing; connector means for releasably retaining said barrel means
in said casing; orifice means in said closed end of said barrel
means for admitting medicine into said barrel means, plunger means
slidably mounted in said barrel means, one end of said plunger means
extending out of said open inner end of said barrel means for gripping
whereby the plunger means can be moved away from said closed outer
end of said barrel means to a loaded position in which medicine
fills the space in said barrel means between said closed outer end
and the other end of said plunger means, said one end of the plunger
means being engageable by said piston, whereby the plunger means
can be moved from the loaded position to a discharge position against
said closed outer end of the barrel means to discharge substantially
all of the medicine from said barrel means.
2. A syringe according to claim 1 wherein said barrel means and
plunger means are tapered slightly from front to rear for insertion
into a similarly tapered casing.
3. A syringe according to claim 1 wherein the interior of the
front end of said barrel means adjacent said orifice means is substantially
conical, and said front end of said plunger means is similarly substantially
conical for ensuring the discharge of substantially all medicine
from said barrel means.
4. A syringe according to claim 1 including needle means detachably
connected to the front end of said barrel means for use in loading
5. A syringe according to claim 4 wherein said needle means is
integral with said barrel means and contiguous with said orifice
6. A syringe according to claim 1 wherein said connector means
includes threads on the outer front end of said barrel means for
connecting said barrel means to an internally threaded casing.
7. A syringe according to claim 6 including wing means on the
front end of said barrel means facilitating mounting of said barrel
means in a casing.
8. A syringe according to claim 1 2 or 3 including teeth means
on the front end of said barrel means around said orifice means
for preventing slipping of said barrel means on the skin of a user.
9. A syringe according to claim 1 including rack means extending
longitudinally of said plunger means; and a projection on said barrel
means for engaging said rack means to provide an indication of movement
of said plunger means relative to said barrel means.
10. A syringe according to claim 1 including nozzle means extending
outwardly from the front end of said barrel means, said nozzle means
containing said orifice means and being adapted to matingly engage
a needle funnel to facilitate loading of the syringe.
11. A syringe according to claim 1 including disposable head means
for mounting on said front end of said barrel means; inset means
in said head means; and an injection orifice in said insert means
for alignment with said orifice means in said barrel means.
12. A syringe according to claim 1 wherein said connector means
includes a bayonet connector at the outer front end of said barrel
means for connecting said barrel means to said casing.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a syringe, and in particular to a syringe
for use with a needleless hypodermic injector.
2. Discussion of the Prior Art
As discussed in the Lindmayer et al U.S. Pat. No. 4342310 issued
on Aug. 3 1982 and in U.S. patent application Ser. No. 485046
filed April 14 1983 the needleless injection of medicines into
the body is decidedly preferable to injection by means of skin piercing
needles. A needleless injector makes a substantially smaller hole
than a needle, and consequently is less painful and results in less
damage than the needle. However, needleless injectors have only
recently begun to achieve public acceptance. A basic reason for
the limited use of such injectors is the difficulties and inconvenience
involved in injecting different medicines using the same injector.
Until now, it was necessary to sterilize an injector used to inject
one medicine before using the same injector for injecting another
medicine. Sterilization was necessary to purge the contaminating
first medicine. Accordingly, for the most part, the use of needleless
injectors has been limited to mass inoculations or other situations,
e.g. the administration of steroids local anaesthetics or insulin
in which the type of medicine is not changed frequently.
Thus, it is readily apparent that a need exists for a device which
permits the extension of needleless injection to situations in which
a variety of medicines are injected into successive patients.
A search of the relevant patent literature reveals that others
are aware of the problem, and that attempts have been made to solve
such problem. In this connection, reference is made to Canadian
Pat. No. 569887 issued to R. P. Scherer on Feb. 3 1969 U.S.
Pat. No. 2635601 issued to E. A. May on April 21 1953; U.S. Pat.
No. 2764977 issued to G. W. Ferguson on Oct. 2 1956; U.S. Pat.
No. 3688765 issued to J. S. Gasaway on Sept. 5 1972; U.S. Pat.
No. 4089334 issued to P. R. Schwebel et al on May 16 1978; and
U.S. Pat. No. 4124024 issued to P. R. Schwebel et al on Nov.
7 1978. Each of these patents describes an injector which utilizes
a disposable ampoule or cartridge containing a single dosage of
medicine. Such devices are unsatisfactory, because it must be possible
to adjust the dosage of most medicines. The dosage required for
any individual is determined, inter alia, by the age and weight
of the individual, and the stage of the illness. Thus, the person
administering the medicine must be able to vary the dosage. The
production and storage of a large number of ampoules or cartridges
containing a variety of dosages of many medicines would be prohibitively
expensive and impractical.
The O. H. Banker U.S. Pat. Nos. 3292621 and 3292622 issued
on Dec. 20 1966 teach the use of an adjustable stroke injection
device and an adjustable unit, respectively. With the first of the
Banker devices, some medicine may remain in the ampoules which can
be quite expensive. Moreover, there is no provision for filling
of the device with different medicines. The other Banker unit must
be sterilized if the medicine being administered is changed.
Accordingly, in spite of the extent of earlier work in this field,
the need still exists for a simple disposable syringe which can
be used for needleless inoculations. An object of the present invention
is to attempt to meet such need by providing a disposable device,
which eliminates the need for sterilization between uses of the
At least one embodiment of the invention prevents the accidental
re-use of a contaminated disposable syringe. Such re-use is possible
with conventional disposable syringes. Moreover, the syringe of
the present invention can be filled accurately to the required dosage,
and, in one form, can be re-used for multiple injections, e.g. when
injecting insulin for the treatment of a diabetic.
GENERAL DESCRIPTION OF THE INVENTION
Accordingly, the present invention relates to a disposable syringe
for use in a needleless injector of the type including a casing,
a piston slidably mounted in the casing for movement between a retracted
position and an extended position, and drive means for driving the
piston from the retracted to the extended position, the syringe
comprising tubular plastic barrel means, said barrel means having
an open rear end for insertion into said casing and a closed front
end for extending out of said casing; orifice means in said front
end of said barrel means for admitting medicine into said barrel
means, plastic plunger means slidably mounted in said barrel means,
a rear end of said plunger means extending out of said open rear
end of said barrel means for gripping whereby the plunger means
can be moved away from said closed front end of said barrel means
to a loaded position in which medicine fills the space in said barrel
means between said closed front end and the front end of said plunger
means, said rear end of the plunger means being engageable by said
piston, whereby the plunger means can be moved from the loaded position
to a discharge position against said closed front end of the barrel
means to discharge substantially all of the medicine from said barrel
In this description and in the appended claims, the term "front"
is used to identify the medicine receiving and injection end of
the barrel or plunger, and the term "rear" is used to
identify the other end of the barrel or plunger.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in greater detail with reference
to the accompanying drawings, which illustrate preferred embodiments
of the invention, and wherein:
FIG. 1 is a schematic side elevation view of one embodiment of
the disposable syringe of the present invention;
FIG. 2 is a longitudinal sectional view of the syringe of FIG.
FIG. 3 is a front end view of the syringe of FIGS. 1 and 2;
FIG. 4 is a rear end view of the syringe of FIGS. 1 to 3;
FIG. 5 is a longitudinal sectional view of the second embodiment
of the syringe of the present invention;
FIG. 6 is a partly sectioned, side elevation view of the syringe
of FIGS. 1 to 4 in a needleless injector;
FIG. 7 is a partly sectioned, side elevation view of a second type
of needleless injector containing a third embodiment of the syringe
of the present invention; and
FIG. 8 is a longitudinal sectional view of the other end of the
injector and syringe of FIG. 7.
DESCRIPTION OF PREFERRED EMBODIMENTS
With reference to FIGS. 1 to 4 one embodiment of the syringe of
the present invention includes a tubular barrel generally indicated
at 1 and a plunger generally indicated at 2. The barrel 1 is defined
by a hollow cylindrical body. The body may taper slightly from a
closed front end 3 to an open rear end 4. The dimensions of a tapered
body need not be as exact as those of a cylindrical body. The barrel
1 is formed of a transparent, plastic material, e.g. polypropylene
of the type used in the barrel of conventional, commercially available
disposable syringes. The plunger 2 is formed of a hard plastic.
External threads 5 are provided on the front end 3 of the barrel
1 for mounting the latter in an injector, as described in greater
detail hereinafter. It will be appreciated that the threads can
be replaced by a bayonet or other type coupling. A pair of diametrically
opposed wings 6 extend radially outwardly the front end 3 of the
barrel 1 for facilitating manual rotation of the barrel 1 during
insertion or removal of the barrel from an injector. A conical nose
8 at the centre of the front end 3 of the barrel contains a longitudinally
extending injection orifice 9. A separable needle 10 extends forwardly
from the nose 8 for loading or filling of the syringe. For such
purpose, an annular groove 11 is provided at the junction between
the rear end of the needle 10 to render the needle 10 frangible.
A cylindrical cap 14 normally protects the needle 10 and the front
injection end of the syringe. The open end of the cap 14 includes
an annular bead 15 which is retained in an annular recess 16 at
the base of the nose 8. Sawtooth projections 18 are provided on
the front end of the barrel 1 for preventing slipping of the syringe
on the skin of a patient. A longitudinally extending, smooth bottomed
slot 19 is provided on each side of the barrel 1. The slot 19 extends
from between the projections 18 to the rear end of the threads 5
so that the interior of the front end 3 of the barrel can easily
be seen from the outside.
The plunger 2 includes a cylindrical body 20 with a conical front
end 21 for abutting the conical interior end 22 of the barrel 1.
The use of mating conical surfaces 21 and 22 ensures that virtually
all of the medicine contained in the chamber 24 is discharged when
the plunger is moved from the rear or loaded position (FIGS. 1 and
2) to the front or discharge position (FIG. 5). An O-ring 25 provides
a fluid-tight seal between the front end of the plunger 2 and the
barrel 1. A pair of concave depressions 27 are provided near the
rear end 28 of the body 20 to facilitate gripping of the plunger
2 during filling. The rear end 28 of the body 20 is protected by
a cylindrical cap 30 until the syringe is about to be used.
Transversely extending lines 32 are provided on the body 20 for
indicating the dosage in the chamber 24. The lines 32 are visible
through a rectangular slot 33 in the side of the reduced diameter
rear end 4 of the barrel 1. A line 35 on one side of the slot 33
provides an accurate reading of the volume of medicine (dosage)
in the chamber 24. A pair of opposed rectangular grooves 36 extend
along substantially the entire length of the body 20. The bottom
37 of each groove 36 has a sawtooth configuration. Small ridges
38 on opposed projections 39 in the rear end 4 of the barrel 1
engage the teeth in the grooves 36. Thus, as the plunger 2 is moved
rearwardly in the barrel 1 and medicine is drawn into the barrel,
and the ridges 38 make a clicking sound as they move over the teeth
in the grooves 36. The teeth correspond to the lines 32 so that
blind patients such as diabetics can measure the dosage by counting
the clicks. Moreover, this arrangement prevents rotation of the
plunger relative to the barrel.
The syringe of FIGS. 1 to 4 is loaded by inserting the needle 10
into a medicine bottle 40 (FIG. 5) and withdrawing the plunger 2.
The syringe of FIG. 5 is the same as that of FIGS. 1 to 4 except
that the front end includes a frusto-conical projection 42 which
has the same taper as the funnel 43 of a conventional disposable
needle 44. The projection 42 contains an insert 45 with the injection
orifice 46 therein. A recess 47 around the projection 42 includes
a thread 48 for securing the flanged end 49 of the needle funnel
43. The end 49 of the funnel 43 is inserted into the recess 47 and
rotated to lock the needle in place. The needle 44 is then inserted
into the medicine bottle 40 and the plunger 2 is partially withdrawn
to fill the barrel 1.
The syringe of FIGS. 1 to 4 or 5 can be used in a variety of injectors
including the injector indicated generally at 50 in FIG. 6. The
injector 50 is similar to the injector described in U.S. Pat. No.
4342310 mentioned hereinbefore, and includes an elongated tubular
casing 51 with a handle 52 and a trigger 53 substantially perpendicular
thereto. A tubular barrel 54 is connected to the front end of the
casing 51. The rear end of the casing 51 defines a compression chamber
55 which contains a substance such as chlorotrifluoromethane which
changes to a liquid when subjected to pressure at normal room temperature,
and changes back to a gas when the pressure is released. There is
sufficient of the substance in the chamber 55 that some liquid is
always present in such chamber.
The rear end 56 of the barrel 54 is threaded for connecting the
barrel 54 to the casing 51. A gasket 57 provides a fluid-tight seal
between the barrel 54 and the casing 51. A piston 58 is slidably
mounted in the compression chamber 55 for longitudinal reciprocating
movement between a rest position and a charged position (FIG. 6)
in which the piston 58 compresses the gas to convert at least a
portion of the gas into a liquid. An O-ring 59 seals the piston
58 with respect to the interior of the handle end of the casing
51. A gasket 60 on the rear, compressions chamber end of the piston
58 seals the chamber 55 from the remainder of the casing 51.
The piston 58 is slidably mounted in the rear end of the barrel
54. An O-ring 62 provides a seal between the piston 58 and the barrel
54. A recess 63 is provided in the front end of the piston 58 for
receiving the rear end 28 of the plunger 20. The front end 64 of
the barrel 54 is internally threaded, so that the barrel 1 of the
disposable syringe can be securely mounted in such barrel 54. In
order to use a thin walled barrel 1 which is capable of resisting
the high pressures required in the barrel 54 to create a high velocity
jet, the front section 65 of the barrel 54 is tapered internally
to match the taper of the syringe barrel 1.
The handle 52 of the injector contains a charging chamber 66 for
a liquid such as an oil. The chamber 66 can be connected to a pressure
chamber 67 between the rear end 68 of the barrel 54 and the rear
end 69 of the piston 58. When the piston 58 moves into the chamber
55 the pressure chamber 67 enlarges to receive liquid from the
charging chamber 66. Liquid from the chamber 66 passes through a
valve defined by a ball 71 and a helical spring 72 which biases
the ball against a seat 74. A rod 76 is slidably mounted in the
chamber 66 for moving the ball 71 upwardly to open the valve. The
bottom end of the rod 76 is connected to a piston (not shown), which
is operated by the trigger 53. Because the piston actuating mechanism
does not form part of the present invention, no details of such
mechanism are provided herein. It is sufficient to know that the
rod 76 is moved by operation of the trigger 53 which is pivotally
connected to the casing 51. The trigger 53 is biased away from the
handle 52 by a spring 78. The trigger 53 is connected to a bar 80
which is slidably mounted in a slot in the front side of the handle
52. The bottom end of the bar 80 (not shown) operates the piston
to move the rod 76 against the ball 71. In order to move the piston
58 rearwardly to the cocked position, it is necessary to pump the
trigger 53 which pumps liquid from the charging chamber 66 into
the pressure chamber 67. Thus, the gas in the compression chamber
55 is compressed and changes into liquid form. In order to administer
medicine, the front end 3 of the barrel 1 is placed against the
skin, and a safety catch 82 on the bottom end of the handle 52 is
rotates 90.degree. to connect the trigger 53 to the rod 76 releasing
the ball 71 when the trigger is pressed. In the manner the piston
58 is released, and moves forward in the barrel 54 the plunger
20 moves forward in the barrel 1 to discharge the medicine, and
the charging liquid returns to the handle 52.
The disposable syringe of the present invention can also be used
with a needleless injector of the type disclosed by Canadian patent
application No. 403840 also mentioned hereinbefore. Referring
to FIGS. 7 and 8 the injector includes a casing generally indicated
at 84. The casing 84 is defined by cylindrical, telescoping front
and rear sections 85 and 86 respectively. The rear section 86 of
the casing 84 is mounted in the front section 85 for movement between
the extended or rest position (FIG. 7) and the retracted position
(FIG. 8). The front section 85 of the casing 84 includes a forwardly
extending neck 87 and an internal cylinder 88 for receiving a syringe
in accordance with the present invention. For such purpose, the
front end 89 of the cylinder 88 is internally threaded for retaining
the externally threaded front end 90 of the barrel 91 of the syringe.
During injection, the front end 90 of the barrel 91 is covered
by an injection head 92. The head 92 includes a cylindrical outer
sleeve 93 which surrounds the neck 87 of the casing 84 and an externally
threaded inner sleeve 94 for connecting the head 92 to the front
end 89 of the cylinder 88. Projections 95 are provided on the disc-shaped
front end 96 of the head 92 for preventing slipping of the injector
on the skin during use. An insert 97 with an injection orifice 98
is provided in the front end 96 of the head 92.
As in the other embodiments of the invention, a plunger 100 is
slidably mounted in the barrel 91 for movement between a front,
rest or discharge position (FIG. 7) and a loaded or filled position
(FIG. 8). The plunger 100 includes a tapered front end 101 and is
sealed in the barrel 91 by an O-ring 102. The rear end of the cylinder
88 carrying the syringe is externally threaded for mounting in an
internally threaded ring 103 which is connected to an annular,
inwardly extending shoulder 104 on the front end of the rear casing
section 86. Rotation of the rear casing section 86 with respect
to the section 85 causes movement of the section 86 into the section
85. Such movement of the rear section 86 into the front section
85 of the casing is limited by a latch mechanism. The latch mechanism
includes a hole 105 and a ball 106 in the rear casing section 86.
When the ball 106 is aligned with the hole 105 the ball is forced
into the hole 105 by a stepped collar 107. The collar 107 and the
ball 106 are mounted in a cup-shaped bushing 108 which is slidable
in the rear casing section 86. A helical spring 110 in the collar
107 biases the collar and the ball 106 towards the rear of the casing
section 86. In the extended position of the casing 84 (FIG. 7),
the ball 106 bears against the interior surface 112 of the casing
section 86. When the ball 106 becomes aligned with the hole 105
the ball is pushed into the hole.
When the casing sections 85 and 86 move together a stack of disc
springs 113 is compressed between the bushing 108 and an end cap
114 on the casing 84. The cap 114 is cup-shaped and externally threaded
for mounting in the internally threaded end 115 of the casing section
86. Opposed rectangular wings 116 are provided near the end 115
of the casing section 86 to facilitate rotation of the section 86.
The injector is actuated, i.e. the bushing 108 is pushed forwardly
by the springs 113 when the sections 85 and 86 are released by
a push button (not shown) in the cap 114. As described in Canadian
patent application No. 403840 the desired injection pressure can
be achieved by providing the appropriate disc springs 113 in series.
In order to move the plunger 100 with the bushing 108 the rear
end 117 of the plunger 100 is bifurcated for engaging the bushing
108. An annular flange or washer 118 on the plunger 100 moves the
bushing 108 rearwardly to engage the springs 113 when the syringe
is inserted into the casing 84. The rear casing section 86 is rotated
counterclockwise to move the front section 85 and the barrel 91
away from the rear section 86. As the casing sections 85 and 86
move apart, the plunger 100 initially moves the barrel 91 because
of the friction of the O-ring 102. The enlarged heads 119 on the
arms at the rear end 117 of the plunger 100 engage the rear surface
of the bushing 108 to prevent movement of the plunger 100 with the
barrel 91. Continued separation of the casing sections 85 and 86
creates a partial vacuum in a chamber 120 (FIG. 8) in the syringe
for receiving medicine.
When filling the syringe, the injection head 92 is removed, and
a bottle holder generally indicated at 122 is placed in the front
end 87 of the casing 84. The bottle holder 122 includes a hollow
cylindrical body 123 with an open bottom end 124 for receiving a
standard medicine bottle 125. Longitudinally extending slots 126
in a skirt portion 127 of the body 123 facilitate insertion of the
bottle 125 into the holder by making the body flexible. A needle
128 extends downwardly from the closed top end 129 of the holder
for puncturing the top end of the medicine bottle 125. An externally
threaded sleeve 130 extends upwardly from the top end 129 of the
holder for connecting the holder to the front end 89 of the cylinder
88. In such position, the sleeve 130 receives a projection 131 on
the front end of the barrel 91 ensuring proper filling of the chamber
This embodiment of the invention is best adapted for the treatment
of diabetics, who generally use one type of medicine only. Injections
can be repeated using the same barrel 91 until such barrel becomes
contaminated at which time the disposable head 92 the barrel 91
and the plunger 100 are replaced with sterile elements.
All of the elements of each embodiment of the invention are stored
in hermetically sealed, sterile plastic bags of the type used for
conventional disposable syringes. The syringe of the present invention
provides a relatively inexpensive, quick means for sterile injections,
without the inconvenience of sterilization. Moreover, the syringe
described hereinbefore is relatively accurate in terms of dosage,
and can be filled from virtually any bottle or vial.