Note: Descriptions are shown in the official language in which they were submitted.
' 'x "" CA 02239515 1998-06-04 ,..r.~
SPRING-ACTUATED NEEDLELESS INJECTOR
Background of the Invention
Field of the Invention
The present invention is directed to the field of medicinal injectors, and,
more
s particularly, to needleless injectors which have spring-actuated pistons
which force
medicinal fluids through the skin without piercing the skin.
Description of the Related Art .
Many systems have been developed for injecting liquid medications into
persons as part of a treatment program, as vaccination against disease, and
for other
io purposes. Many such medications are injected into the tissues under the
skin rather
than directly into a blood vessel. The medications thus injected are then
absorbed by
the circulatory system and transported throughout the body. Such intramuscular
injections are used, for example, in the treatment of diabetes. Typically, an
injection
is made using a hypodermic syringe having a needle which pierces the skin so
that the
~ s medication forced from the syringe is injected into the underlying tissue.
For many persons, the very thought of receiving an injection in this manner is
uncomfortable at best and often frightening. Thus, needleless injectors have
been
developed to obviate the use of needles. Such needleless injectors apply a
high
pressure to a medicinal fluid in a syringe to force the fluid out of a small
orifice at the
Zo end of the syringe. When the orifice of the syringe is held against the
skin, the fluid
penetrates the skin and enters the underlying tissues where it is absorbed as
discussed
above.
Various systems for applying the pressure to the fluid in the syringe have
been
developed. Some needleless injectors have used high pressure gas, such as, for
is example, carbon dioxide (COZ). Other injectors have used springs to force
the fluid
out of the syringe. The present invention is directed to improvements to
spring-
actuated needleless injectors.
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Summary of the Invention
One aspect of the present invention is a needleless injector which injects
medication through the skin of a patient. The needleless injector comprises a
vial
which holds a volume of liquid medication. The vial comprises a vial piston
which
s moves to force the liquid medication out of the vial. A power mechanism
applies
force to the vial piston. The power mechanism comprises a power piston which
has
a plurality of ratchets formed thereon. A spring has a first end and a second
end,
wherein the first end of the spring is positioned to apply force to the power
piston.
A trigger engages the ratchets on the power piston to hold the power piston in
place
~ o against the force applied by the spring. The trigger selectively releases
the power
piston to move in response to the force applied by the spring. The power
piston
applies the force to the vial piston to cause the vial piston to force the
liquid
medication out of the vial. A cocking mechanism applies force to the power
piston
to move the power piston against the force of the spring to engage the
ratchets. A
~ s travel adjustment mechanism is moveable to position the second end of the
spring
within the power mechanism to control the movement of the power piston,
thereby
controlling the volume of liquid ejected from the vial. Preferably, the travel
adjustment mechanism comprises a threaded plug, and the power mechanism
comprises a threaded bore. The threaded plug is rotatable in the bore to move
the
ao threaded plug closer to and further away from the vial to thereby limit the
distance by
which the power piston can be moved away from the vial when cocked. Also
preferably, the ratchets on the power piston are spaced apart by equal
distances, with
each of the ratchets corresponding to an incremental volume of the vial. In
particularly preferred embodiments, the travel adjustment mechanism is
adjustable for
2s a predetermined volume of liquid medication to cause the power piston to
engage the
vial piston to prevent a vial from being inserted into the power mechanism
with a
volume of liquid medication greater than the predetermined volume.
Another aspect of the present invention is a medication vial for needleless
injection of a liquid medication into a patient. The medication vial comprises
a
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container which defines a volume which receives a quantity of liquid
medication. The
container has a first end and a second end, and the first end has an orifice
formed
therein to release the liquid medication. A piston having a first end and a
second end
moves within the container. The first end of the piston is moveable with
respect to
s the first end of the container to define the volume when the first end of
the piston is
moved away from the first end of the container. The piston forces the liquid
medication through the orifice when the first end of the piston is moved
toward the
first end of the container. The first end of the piston has a protuberance
formed
thereon which closes the orifice to block further use of the container after
the liquid
~ o medication is expelled.
Another aspect of the present invention is a stroke adjustment mechanism in
a spring-powered needleless injector. The needleless injector has a piston, a
spring
to power the piston, and a trigger mechanism to selectably hold the piston
against the
spring and to release the piston to move in response to force provided by the
spring.
i s The piston is coupled to a vial of liquid medication to force liquid
medication from
the vial. The stroke adjustment mechanism comprises a plurality of ratchets
formed
on the piston. Each ratchet is selectably engageable with the trigger
mechanism to
select a stroke distance for the piston. An adjustment plug is moveable within
the
needleless injector. The adjustment plug is engageable with a first end of the
spring
zo and with a first end of the piston to control an amount of compression of
the spring
when the piston is engaged with the trigger mechanism. The adjustment plug
further
limits an amount of travel of the piston to thereby limit an amount of liquid
medication ejected from the vial. Preferably, the adjustment plug comprises a
threaded portion and an extended portion. The threaded portion has a shoulder
which
zs engages the spring. The extended portion engages the piston such that the
spring is
compressed between the piston and the shoulder. Also preferably, the extended
portion of the adjustment plug includes a central bore. The stroke adjustment
mechanism further includes an adjustment knob. The adjustment knob includes a
manual engagement portion rotatable by a user and an extended portion. The
so extended portion of the adjustment knob engages the central bore of the
extended
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portion of the adjustment plug to thereby rotate the adjustment plug when the
engagement portion is rotated.
According to an aspect of the present invention, there is provided a
needleless
injector which injects medication through the skin of a patient, the
needleless injector
S comprising:
a vial which holds a volume of liquid medication, the vial comprising a vial
piston which moves to force the liquid medication out of the vial; and
a power mechanism which applies force to the vial piston, the power
mechanism comprising:
a power piston, the power piston having a plurality of ratchets formed
thereon;
a spring having a first end and a second end, the first end of the spring
positioned to apply force to the power piston;
a pair of triggers which engage the ratchets on the power piston to hold the
power piston in place against the force applied by the spring and which
selectively
release the power piston when both triggers are squeezed, allowing the power
piston
to move in response to the force applied by the spring, the power piston
applying the
force to the vial piston to cause the vial piston to force the liquid
medication out of the
vial;
a cocking mechanism, the cocking mechanism applying force to the power
piston to move the power piston against the force of the spring to engage the
ratchets;
and
a travel adjustment mechanism, the travel adjustment mechanism moveable to
position the second end of the spring within the power mechanism to control
the
movement of the power piston, thereby controlling the volume of liquid ejected
from
the vial.
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Brief Description of the Drawings
The present invention will be described below in connection with the
accompanying drawing figures in which:
Figures 1 andl A illustrate perspective views of the needleless injector of
the
present invention;
Figure 2 illustrates an exploded view of the needleless inj ector of the
present
invention;
Figure 3 is a cross-sectional view of the needleless injector of Figures 1 and
lA taken along the lines 3-3 in Figure 1, showing the needleless injector with
a vial of
having a substantially full volume of liquid in position and with the power
mechanism
cocked for operation;
Figure 4 is a cross-sectional view of the needleless injector of Figures 1 and
lA taken along the lines 4-4 in Figure lA, showing the needleless injector
with a vial
of liquid in position and with the power mechanism cocked for operation;
Figure S is cross-sectional view of the needleless injector of Figure 1,
similar
to the view of Figure 3 but with the vial removed, which illustrates the
action of
cocking the power mechanism to prepare the injector to receive a vial having
approximately half of the maximum volume of liquid medication;
Figure 6 is a cross-sectional view of the needleless injector of Figure 1,
similar
to the view of Figure 3, showing the ejection of the liquid medication when
the piston
is moved by the springs;
Figure 7 is an enlarged cross-sectional view of the vial of Figure I in
position
against the skin of a patient pictorially illustrating the flow of the liquid
medicine into
the tissues of the patient;
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Figure 8 is an enlarged cross-sectional view of the vial as in Figure 6
showing
the plugging effect of the end of the piston to preclude further use of the
vial;
Figure 9 is an enlarged cross-sectional view of the end of the vial in Figure
8
showing the plugging effect in more detail;
s Figure 10 is a cross-sectional view of the needleless injector similar to
Figure
3, showing the dose adjustment stop moved to permit only a vial having a small
dose
of liquid medicine to be inserted into the needleless injector;
Figure I1 is a cross-sectional view of the needless injector of Figure 10 with
the vial of liquid medicine in position to be ejected;
~o Figure 12 is a cross-sectional view of the needleless injector similar to
Figure
3, showing the dose adjustment stop moved and the injector cocked to permit a
vial
having a maximum dose of liquid medicine to be inserted into the needleless
injector;
Figure 13 is a cross-sectional view of the needless injector of Figure 12 with
the vial of liquid medicine in position to be ejected;
i s Figure 14 is a cross-sectional view of an alternative embodiment of the
needleless injector having a quarter-turn engagement mechanism between the
vial and
the power mechanism, and further having a modified orifice;
Figure 15A is a front elevational view of the needleless injector of Figure 15
showing the positioning of the vial onto the power mechanism prior to turning
the vial
2o to lock the vial to the power mechanism;
Figure 15B is a front elevational view of the needleless injector of Figure 15
showing the positioning of the vial after turning the vial to lock the vial to
the power
mechanism;
Figure 16 is an enlarged cross-sectional view of a portion of the vial showing
zs the modified orifice and the protuberance surrounding the inner portion of
the orifice;
and
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Figure 17 further illustrates the enlarged cross-sectional view of Figure 16
and
shows the engagement of the funnel-shaped recess on the piston with the
protuberance
around the orifice to squeeze the orifice closed when the piston is driven
forward.
Detailed Description of the Preferred Embodiment
s Figures l and 1 A illustrate perspective views of a preferred embodiment of
a
needleless injector 100 in accordance with the present invention. (Figure lA
is
substantially the same as Figure 1 and is included to provide the section
lines for
Figure 4.) The needleless injector 100 comprises a power mechanism 102 and a
medication vial 104. As illustrated in the exploded perspective view in Figure
2, the
~ o medication vial 104 includes a threaded portion 106 which threadingly
engages a
threaded socket 108 of the power mechanism 102.
As shown more clearly in Figure 2, the power mechanism 102 further includes
a bar-shaped main body portion 120 which has a generally oval-shaped cross-
section.
The main body portion 120 is shown lying on its side in Figures 1 and 2
wherein an
~ s oval-shaped top end 122 has the socket 108 which receives the medication
vial 104.
The body portion 120 has an oppositely disposed oval-shaped bottom end I24.
The
body portion 120 has a first wide side 126 and an oppositely disposed second
wide
side 128. The body portion 120 has a first narrow side 130 and an oppositely
disposed second narrow side 132.
zo A first trigger slot 150 is formed in the first narrow side 130 to receive
a first
trigger 152. As shown more clearly in Figure 3, the first trigger 152 is
pivotably
mounted proximate to its midpoint on a pin 154 which is pressed into a hole
156
through the first wide side 126, through a hole 157 in the trigger 152, and
into a
corresponding hole (not shown) in the second wide side 128. The first trigger
152 has
zs an activation portion 158 and a ratchet portion 160. A spring 162 biases
the first
trigger 152 so that the activation portion 158 is forced out of the first
narrow side 130
and so that the ratchet portion 160 is forced into the first narrow side 130.
Similarly, a second trigger slot 170 is formed in the second narrow side 132
to receive a second trigger 172. The second trigger 172 is pivotably mounted
on a pin
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174 which is pressed into a hole (not shown) through the second-wide side 128,
through a hole 177 in the trigger 172, and into a corresponding hole (not
shown) in
the second wide side 128. The second trigger 172 has an activation portion 178
and a
ratchet portion 180. A spring 182 biases the second trigger 172 so that the
activation
portion 178 is forced out of the second narrow side 132 and so that the
ratchet portion
180 is forced into the second narrow side 132.
A slot 200 is formed into the first wide side 126. The slot 200 has a width on
the first wide side 126 sufficient to receive a first sleeve spring 202. The
width of the
slot 200 at the first wide side 126 extends for a depth slightly greater than
the
diameter of the first sleeve spring 202 so that the first sleeve spring 202
can be
positioned in the slot 200 without an portion extending above the first wide
side 126.
The width of the slot 200 narrows below the first sleeve spring 202 to a width
less
than the diameter of the first sleeve spring 202 so that first sleeve spring
202 is
supported just below the first wide side 126. The narrow portion (not shown)
of the
1 S first slot 200 extends through the body portion 120 to the second wide
side 128.
A slot 204 substantially similar to the slot 200 is formed into the second
wide
side 128 to receive a second sleeve spring 206. The wide portion of the second
slot
204 is not shown. The narrow portion of the second slot 204 is shown extending
through the first wide side 126.
With the sleeve springs 202 and 206 in position, a cocking sleeve 220 is
positioned over the body portion 120. The cocking sleeve 220 has a generally
oval-
shaped cross-section and is sized so that it fits over the body portion 120
and moves
freely thereon from the top to the bottom without significant lateral play.
The cocking
sleeve has a top end 222, a bottom end 224, a first wide side 226, a second
wide side
228, a first narrow side 230 and a second narrow side 232. A pair of slots 240
and 242
formed on the first narrow side 230 and the second narrow side 232,
respectively, of
the cocking sleeve 220 proximate to the top end 222. The slots 240, 242 have a
sufficient width to encompass the activation portions 158 and 178 of the first
trigger
152 and the second trigger 172, respectively. The cocking sleeve 220 further
includes
a pair of holes 250 and 252 extending from the first wide surface 226 to the
second
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wide surface 228. When the cocking sleeve is in position on the body portion
120, the
holes 250 and 252 are aligned with the ends of the slots 200 and 204,
respectively. A
pair of pins 254 and 256 are positioned in fhe holes 250 and 252, and extend
thus
through the slots 200 and 204. The pins 254 and 256 engage respective first
ends of
the sleeve springs 202 and 206. The operation of the cocking sleeve 220 and
the
sleeve springs 202 and 206 will be discussed below.
As shown in the cross-sectional views in Figures 3 and 4, the body portion 120
has a cylindrical bore 300 extending from the bottom end 124 to the top end
122. An
upper portion 302 of the central bore 300 proximate to the top end 122 has a
largest
diameter and is threaded to form the socket 108 which receives the medication
vial
104. A lower portion 304 of the cylindrical bore 300 proximate to the bottom
end 124
a slightly smaller diameter. A lowermost portion of the lower portion 304 is
threaded
to receive an adjustment plug described below. A second portion 304 is not
threaded.
A middle portion 306 of the cylindrical bore 300 just below the upper portion
302
(i.e., to the left of the upper portion 302 in Figures 3 and 4) has a smaller
diameter
sized to receive a vial piston described below.
A piston 310 is positioned in the central bore 300. The piston 310 has a first
end 312 and a second end 314. The first end 312 is positioned in the direction
toward
the bottom end 124 of the body portion 120, and the second end 314 is
positioned in
the direction of the top end 122. The piston 310 has an outside diameter
selected to be
slightly smaller than the inside diameter of the cylindrical bore 300 so that
the piston
310 moves freely within the cylindrical bore 300 without significant play.
A first portion 316 of the piston 310 proximate to the first end 312 is
generally
smooth. A second or ratchet portion 318 of the piston 310 proximate to the
second
end 314 is milled or otherwise shaped to form a series of ratchets 320. In
particular,
the ratchet portion 318 shown in Figure 3 has ten ratchets 320 formed thereon.
Each
of the ratchets 320 is tapered inward in the direction of the bottom end 124
of the
body portion 120 to form a shoulder 322. As illustrated in Figure 3, the
ratchet
portions 160 and 180 of the first trigger 152 and of the second trigger 1?2
are formed
at an angle to generally match the taper of the ratchets 320 and to engage the
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shoulders 322. The operation of the ratchet portion 318 of the piston 310 with
respect
to the triggers 152 and 172 will be explained below.
A compression spring 330 is positioned in the cylindrical bore 300 below the
piston 310. A first end 332 of the compression spring 330 rests against the
first end
312 of the piston 310. A second end 334 of the compression spring 330 is
positioned
in a direction toward the bottom end 124 of the body portion 120.
A stroke adjustment plug 340 is positioned in the cylindrical bore 300 below
the compression spring 330. The stroke adjustment plug 340 has a first portion
342
having a threaded outside diameter sized to fit within the cylindrical bore
300 and to
engage the threaded portion of the cylindrical bore proximate to the bottom
end 124
of the body portion 120. The stroke adjustment plug 340 has a second extended
portion 344 which extends from the first portion 342 in the direction toward
the top
end 122 of the body portion 120. The compression spring 330 is positioned over
the
extended portion 344 such that the second end 334 of the compression spring
330
rests against a shoulder 346 of the first portion 342 of the stroke adjustment
plug 340.
The stroke adjustment plug 340 has a central bore 348 formed therein. The
central bore 348 of the stroke adjustment plug 340 preferably has a square
cross
section or any other non-circular cross section for the reasons set forth
below. A
stroke adjustment knob 350 is mounted in the cylindrical bore 300 proximate to
the
bottom end 124. A first portion 352 of the knob 350 is a generally square bar
portion
which has a cross section sized to fit within the central bore 348 of the
stroke
adjustment plug 340. A second portion 354 of the knob 350 is generally
cylindrical
and is sized to fit within the cylindrical bore 300 of the body portion 120.
The second
portion 354 has a groove 356 formed therein. As shown in Figure S, a set screw
360 is
positioned through a hole 362 in the first side 130 of the body portion 120 to
engage
the groove 356 in the second portion 354 of the knob 350. The set screw 360 is
initially threaded into the hole 362 sufficiently far to hold the knob 350 so
that the
second portion 354 cannot be removed from the cylindrical bore 300 but not so
far as
to press against the inside diameter of the groove 356. Thus, the knob 350 can
turn
within the cylindrical bore 300.
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A third portion 358 of the knob 350 is generally cylindrical and has a size
greater than the size of the cylindrical bore 300. The third portion 358 has a
shoulder
thereon which rests against the bottom end 124 of the body portion when the
second
portion 354 is inserted into the cylindrical bore 300. The outside diameter of
the third
s portion 358 is preferably knurled to provide a surface which can be readily
gripped
by a person's fingers so that the knob 350 can be turned. As will be discussed
in
more detail below, as the knob 350 is turned, the stroke adjustment plug 340
is turned
by the interaction of the first portion 352 of the knob 350 and the central
bore 348 of
the stroke adjustment plug 340. Thus, as the knob 350 is turned, the stroke
~o adjustment plug 340 will be threaded up or down the central bore 300. The
stroke
adjustment plug 340 will slide on the first portion 352 of the knob 350 so
that the
knob 350 only needs to rotate and does not move up or down with respect to the
central bore 300.
As illustrated in Figure 3, the medicinal vial I04 comprises a cylindrical
15 portion 400 having an inside diameter. A first end 402 of the cylindrical
portion 400
is substantially closed with only a small opening 404 formed therein. A second
end
406 of the cylindrical portion 400 proximate to the threaded portion 106 is
open for
the full inside diameter. A piston 410 is positioned within the cylindrical
porEion 400
through the second end 406. The piston 410 has a main body portion 412 sized
to fit
Zo within the cylindrical portion 400 and to move freely therein. A first end
414 of the
piston 410 proximate extends from the cylindrical portion 400 for engagement
with
the piston 310, as described in more detail below. Preferably, as illustrated,
the piston
410 comprises a solid plastic.
The piston 410 has a second end 418 which is positioned within the cylindrical
~s portion 400. The second end 418 has an outside diameter smaller than the
inside
diameter of the cylindrical portion 400. A rubber piston ring 420 is
positioned on the
second end 418. The rubber piston ring 420 is sized to fit tightly within the
cylindrical portion 400 to form a seal therein while still permitting movement
within
the cylindrical portion 400. Thus, as illustrated in Figure 3, a liquid
medicine 422 is
so constrained between the first end 414 and the rubber piston ring 420.
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As further illustrated in Figure 3, the opening 404 at the first end 402 of
the
cylindrical portion 400 is tapered such that the outer portion of the opening
404 at the
outside surface of the cylindrical portion 400 has a diameter selected to
control the
flow of medicinal liquid from the cylindrical portion 400. For example, an
opening
404 having a diameter of approximately 0.006 inch has been advantageous in one
embodiment. The opening 404 is funnel shaped with its largest diameter inside
the
cylindrical portion 400 and its smaller diameter at the surface.
The second end 418 of the piston 410 has a central extended portion 430
which is aligned with the opening 404 in the cylindrical portion 400. The
extended
portion 430 has an outside diameter that is smaller than the inside diameter
of the
opening 404 within the cylindrical portion 400. However, the outside diameter
of the
extended portion 430 is smaller than the inside diameter of the opening 404 at
the
surface. Preferably, the extended portion 430 has a funnel-shaped recess 432
formed
therein so that the extended portion 430 has relatively thin walls at the end
proximate
to the opening 404 and has thicker walls proximate to the piston ring 420.
When the present invention is assembled as illustrated in Figures 1, 3 and 4,
it
operates to provide a high pressure needleless injection system. In operation,
the vial
104 is first filled with an appropriate liquid medicine, such as, for example,
insulin.
The vial 104 is provided as a sterile one-use-only vial. In one embodiment,
the vial
104 is filled in a pharmaceutical environment by dispensing an appropriate
amount of
the liquid medicine in the vial 104 and then inserting the piston 410 into the
cylindrical body portion 400 to seal the liquid therein. The first end 402 is
then sealed
in an appropriate manner, and the filled vial 104 is packaged for
distribution.
Alternatively, the vial 104 can be filled by a health care provider or, for
self
injections of insulin and the like, by a patient. The vial 104 is shipped in
sterile
packaging (not shown). The vial 104 is removed from the sterile packaging and
the
first end 402 is inserted into a source of liquid medication. While holding
the first
end402 of the vial 104 in the medication, the first end 414 of the piston 410
is pulled
slowly to pull the piston 410 away from the first end 402 to thereby draw the
liquid
medicine into the vial 104 in a manner similar to filling a hypodermic
syringe. The
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vial 104 is preferably filled initially with more than the desired volume of
medication,
and the excess volume will be ejected, as discussed below, prior to injecting
the
medication into the patient. In preferred embodiments, the vial 104 is
provided with
conventional markings 500 (Figure 1) to indicate the volume of liquid in the
vial 104.
For example, the markings may be spaced to indicate 0.05 milliliter increments
in
volume. In a preferred embodiment, the vial 104 has a total volume of 0.5
milliliters
and thus has ten markings thereon.
In a further alternative embodiment (not shown), the vial 104 can be
distributed with a needle (not shown) attached to it so that it can be filled
from
sources of liquid medications which need to be punctured by a needle. See, for
example, U.S. Patent No. 4,680,027, which illustrates a removable needle. The
needle
is removed before engaging the vial 104 with the power mechanism 102.
Before engaging the vial 104 with the power mechanism 102, the power
mechanism 102 is cocked to provide the pressure and stroke required to eject
the
liquid medication from the vial 104 for a particular volume of liquid
medication. As
illustrated in Figure 5, this is accomplished by moving the cocking sleeve
downward
(in the direction from the top end 122 to the bottom surface 120). The pins
254 and
256 are positioned proximate to the second end 314 of the piston 310 when the
piston
310 is in its rest (uncocked) position. When the cocking sleeve 220 is moved
toward
the bottom end 124 of the body portion 120, the sleeve 220 causes the pins 254
and
256 to slide in the slots 200 and 204 against the force of the sleeve springs
202 and
206. The pins 254 and 256 push the piston~310 downwardly in the bore 300
toward
the bottom end 124 of the body portion 120 against the pressure of the
compression
spring 330. As the piston 310 moves toward the bottom end 124, the ratchet
ends 160
and 180 of the triggers 152 and 172 are forced outwardly by the taper of each
ratchet
320 and then snap inward behind each shoulder 322. Thus, the ratchet ends 160
and
180 engage each shoulder 322 and operate to hold the piston 310 in position
against
the pressure of the compression spring 330.
The spacing between the shoulders 322 of the ratchets 320 is selected to
provide a predetermined incremental increase in the volume of the vial 104
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' _ -'' CA 02239515 1998-06-04 ""
accommodated by the power mechanism 102. For example, in the preferred
embodiment, each the distance between each shoulder 322 corresponds to a 0.05
milliliter increase in the volume of the vial 104. Thus, by listening to or
feeling the
interaction of the ratchet ends 160 and 180 with the ratchets 320, the user
can cock
s the power mechanism to a distance corresponding to the desired volume of
medicinal
liquid to be ejected from the vial 104. In the preferred embodiment described
herein,
the power mechanism 102 includes an adjustment so that the user does not have
to
rely solely on counting the number of clicks. This feature is described below.
After the piston 310 has been moved to its cocked position, the cocking sleeve
To 220 is released and is returned to its original position, as shown in
Figure 1, by the
pressure of the sleeve springs 202 and 206. The ratchet ends 160 and 180 of
the
triggers 152 and 172 hold the piston 310 in its cocked position.
When the vial 104 is inserted into the power mechanism 102, the first end 414
of the piston 410 contacts the second end 314 of the piston 310. If the vial
104 has
~ s been filled with more liquid than can be accommodated by the position of
the piston
310, then, as the vial is screwed into the power mechanism 102, the first end
414 of
the piston 410 will contact the second end 314 before the threaded portion 106
is fully
seated in the socket 108. Thus, the piston 410 will move in the body portion
400 and
force the excess liquid out of the vial 104.
2o As illustrated in Figure 6, when the activation portions 158 and 178 of the
triggers 152 and 172 are pressed by the user, the ratchet portions 160 and 180
are
disengaged from the ratchets 320. The pressure of the compression spring 330
operates against the first end 312 of the piston 310 to force the piston 310
toward the
upper end 122 of the body portion 120. The second end 314 of the piston 310
as operates against the first end 414 of the piston 410 to force the piston
410 further into
the body portion 400 of the vial 104 and thereby force the liquid medication
422 out
of the vial 104 through the opening 404 as illustrated in Figure 6.
By providing the two opposing triggers 152 and 172, the power mechanism
102 of the present invention requires the user to press both activation
portions 158 and
so 178 to release the piston 310. This safety feature reduces the likelihood
that the
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power mechanism 102 will be accidentally triggered before the user has the
vial 102
in place on the patient's skin and is ready to trigger the mechanism.
When the piston 310 has moved to its full length of travel, the forward motion
of the piston 310 is stopped by metal outcroppings 510 which remain after
forming
the middle portion 306 of the central bore 300 and which extend above and
below the
middle portion 306 between the two slots 200 and 204. Because of the location
of the
section lines 4-4 in Figure lA, the outcroppings 510 are shown in phantom in
Figure
4. The outcroppings 510 prevent the second end 314 of the piston 310 from
striking
the pins 254 and 256 when the piston 310 reaches the end of its travel.
As further illustrated in Figure 7, when the end 402 of the vial 104 is pushed
against the skin 600 of a patient and the triggers are activated, the liquid
is forced out
of the opening 404 with sufficient force to penetrate the skin 600 of a
patient and to
penetrate the tissues 602 beneath the skin 600. As illustrated in Figure 8 and
Figure 9,
when the liquid has been fully expelled from the vial 104 as the piston 410
travels to
the end of the body portion 400, the extended portion 430 enters the funnel
shaped
inside portion of the opening 404. The relatively thin walls of the extended
portion
430 caused by the funnel-shaped recess 432 engage the inside walls of the hole
404
and force the hole 404 closed. The vial 104 and the piston 410 are preferably
formed
from medical-grade plastic. The force of the engagement between the extended
portion 430 and the inner wall of the hole 404 is sufficient to cause the two
parts to
mesh, thereby effectively preventing the vial 104 from being reused.
As discussed above, it is preferred that the power mechanism 102 be cocked
so that the first end 414 of the piston 410 just engages the second end 314 of
the
piston 310 when the vial 104 is inserted into the power mechanism 102. If, the
power
mechanism is not cocked far enough, a portion of the liquid medication will be
forced
out of the vial 104 as the vial 104 is inserted into the socket 108, thus
reducing the
medication to less than the proper dosage. If, on the other hand, the power
mechanism
is cocked too far, the first end 414 of the piston 410 will not touch the
second end
314ofthe piston 310. Thus, when the triggers 152 and 172 are activated, the
piston
310 will travel a short distance and will be traveling a significant velocity
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CA 02239515 2005-04-04
before engaging the first end 414 of the piston 410. This can have the
undesirable
effect of causing the piston 310 to slap against the first end 414 of the
piston 410 and
may cause the user to fail to hold the end 402 of the vial 104 against the
skin. Thus,
the liquid medication 422 may tend to spray on the skin rather than to
penetrate the
skin as desired.
The present invention includes a mechanism to reproducibly match the
position of the cocked piston 310 to the first end 414 of the piston 410. In
particular,
the stroke adjustment plug 340 permits the user to set the stroke of the
piston 310 to
the precise amount of the liquid medication to be dispensed so that when the
vial 104
is engaged with the power mechanism 102, the first end 414 of the piston 410
will rest
on the second end 314 of the piston 310. Thus, when the power mechanism 102 is
triggered, the piston 310 will accelerate the piston 410 to smoothly force the
liquid
medication 422 out of the opening 404.
As illustrated in Figure 10, the stroke adjustment plug 340 is shown in a
position so that the piston 310 can be moved by only the distance of two
ratchets. The
user places the stroke adjustment plug 340 in the position of Figure 10 by
turning the
knurled knob 350 clockwise with respect to the bottom end 124 of the body
portion
120. The stroke adjustment knob 350 turns within the central bore 300 causing
the
first portion 352 (i.e., the square bar) to turn. The first portion 352 is
engaged with the
central bore 348 of the stroke adjustment plug 340. Thus, as the stroke
adjustment
knob 350 turns, the stroke adjustment plug 340 turns within the central bore
300. The
threaded engagement of the stroke adjustment plug 340 with the central bore
300
causes the stroke adjustment plug 340 to advance toward the top end 122 of the
body
portion 120 to the position shown in Figure 10. The user can readily determine
the
correct position to place the stroke adjustment plug 340 by cocking the power
mechanism 102 the required number of clicks (e.g., one click for 0.05
milliliters of
medication, two clicks for 0.1 milliliter of medication, and so on). While the
piston
310 is maintained in the cocked position, the stroke adjustment knob 350 is
turned
until the user feels resistance when the stroke adjustment plug 340 engages
the first
end 312 of the piston 310. The stroke adjustment plug 340 is then
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CA 02239515 2005-04-04
left in this position. Thus; each time the power mechanism 102 is cocked by
moving
the cocking sheath 220 toward the bottom end 124, as shown, the piston 310
cannot
be ratcheted beyond the position established by the stroke adjustment plug
340.
When the vial 104 is engaged with the power mechanism 102 when adjusted
as in Figure 10, the vial 104 can hold a maximum of 0.1 milliliters as
illustrated in
Figure 11. Any excess medication will be ejected as the vial 104 is engaged,
as
discussed above.
In the event that the user does not want to make further adjustments to the
stroke of the power mechanism 102, the stroke adjustment knob 350 may be
removed
by retracting the screw 360, or, in the alternative, the screw 360 may be
further
engaged in the hole 362 until the end of the screw 360 frictionally engages
the groove
356 so that the knob 350 cannot be turned.
Figure 12 further illustrates the adjustment of the present invention, wherein
the stroke adjustment plug 340 is positioned for maximum discharge of
medication
(e.g., 0.5 milliliter). Figure 13 illustrates the vial 104 in position in the
power
mechanism 102 when the power mechanism 102 has been cocked as illustrated in
Figure 12.
The stroke adjustment plug 340 has the further advantage that the force
applied to the liquid medication for the initial injection of the medication
through the
skin is substantially the same regardless of the volume of the liquid to be
ejected. In
particular, as illustrated in Figures 6, 11 and 13, the compression spring 330
is
compressed by substantially the same amount between the first end 312 of the
piston
310 and the first portion 342 of the stroke adjustment plug 340. Thus, when
the piston
310 is first released, the force initially applied to the piston 310 and thus
to the liquid
medication 422 is substantially the same for each volume.
The needleless injector of the present invention can be manufactured in other
configurations. For example, Figures 14-17 illustrated an alternative
embodiment of
the needleless injector 700 in which a vial 702 can be more quickly engaged
onto a
power mechanism 704. The embodiment of Figures 14-17 further includes a
modified
first end 710 of the vial 702 to assure that an orifice 712 is fully closed
after the vial
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' - - CA 02239515 1998-06-04 ""-
is emptied. Other than as described herein, the embodiment 700 of Figures I4-
16 is
substantially similar to the previously described embodiment, and like
elements are
numbered the same.
As illustrated in the cross-sectional view of Figure 14 and in the front
s elevational views in Figures I SA and I SB, the vial 702 engages the power
mechanism
704 via a quarter-turn engagement mechanism comprising a first thread 720 and
an
oppositely disposed second thread 722 formed on a second end 724 of the vial
702.
Each of the threads 720 and 722 extends for approximately one-fourth of the
circumference of the second end 724 of the vial 702. The threads 720 and 722
have
i o pitches selected to match corresponding threads 730 and 732 formed in a
first end
734. The threads 730 and 732 are conventional double lead threads which enable
both
threads 720 and 722 of the vial 702 to be engaged at the same time. By turning
the
vial 702 one-quarter turn in the clockwise direction, as viewed in Figures 15A
and
15B, the vial 702 is fully engaged with the power mechanism 704, thus enabling
the
~ s user of the present invention to rapidly switch vials. This feature is
particularly
advantageous for mass inoculations of vaccine, and the like.
As illustrated more clearly in the enlarged view of Figure 16, the vial 702 in
accordance with the embodiment of Figures 14-16 has the modified orifice 712.
In
particular, the orifice 712 extends into a cavity 740 of the vial 702. An
inner wall 742
20 of the vial 702 is formed into a conical protuberance 744 which surrounds
the
innermost portion of the orifice 712. The conical protuberance 744 is sized to
have
a initial outside diameter than the inside diameter of the funnel-shaped
recess 432 on
the extended portion 430 of the piston 410. Thus, when the piston 410 is
driven
forward by the power mechanism 704, the funnel-shaped recess 432 engages the
is outside of the conical protuberance 744 and squeezes the orifice 712
closed, as
illustrated in Figure 17.
As further illustrated in Figure 16, the inner wall 742 of the vial 702
proximate
to the orifice 712 is sloped generally toward the orifice 712, and the
protuberance 744
extends from the sloped portion of the inner wall 742.
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..~.
CA 02239515 1998-06-04
In one embodiment of the present invention, the various portions of the power
mechanism 102 are fabricated 'from aluminum or other suitable metal, as
indicated in
cross-section herein. Alternatively, the power mechanism 102 may be fabricated
from
high impact plastic to reduce the cost and the weight of the mechanism.
Preferably,
s the vial 104 and its component elements are fabricated from a medical grade
plastic
such as is conventionally used in hypodermic syringes and the like.
The invention may be embodied in other specific forms without departing from
its spirit or essential characteristics. The described embodiments are to be
considered
in all respects only as illustrative and not restrictive. The scope of the
invention is
~ o therefore indicated by the appended claims rather than by the foregoing
description.
All changes which come within the meaning and range of equivalency of the
claims
are to be embraced within that scope.
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