Note: Descriptions are shown in the official language in which they were submitted.
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DEVICE FOR HYPODERMIC INJECTION WITHOUT NEEDLE OF A MEDICINE IN LIQUID
FORM
The present invention relates to a device for sub-cutaneous injection of a
liquid medication without using a needle. It relates more particularly to a
device of the
above kind of the type which comprises a) an injection head consisting of a
tubular body
delimiting a chamber adapted to contain a volume of said medication and closed
at one
end by a transverse wall through which passes at least one microchannel
opening onto
an outside face of the head designed to be applied to the skin of a patient
and at the
other end by a piston mobile axially in said chamber, b) means for filling the
chamber,
and c) means for acting on said piston to force said medication out of the
injection head
via said microchannels.
A device of the above type is disclosed in international patent application
WO 95/24176, which concentrates more particularly on the means for filling the
chamber of the injection head with a volume of the medication to be
administered. As
shown in figure 1 of the appended drawing, those means essentially comprise a
device 1
formed of a tubular cylindrical body 2 containing a cartridge 3 filled with
medication and
equipped at one end with a piston 4 that can slide in the cartridge 3 when
pressure is
applied to it by an operating rod 5 projecting from one end of the body. The
other end of
the cartridge 2 is closed by a seal 6.
The end of the body 2 opposite the end 5 is closed by a bush 7 through
which passes axially a hollow needle 8 opening into the interior of the
tubular body 1.
In a first position (not shown in figure 1), the cartridge 3 is spaced from
the
tip of the needle 8, which therefore does not pass through the seal 6. To
discharge its
contents into an injection head 9 mounted on the bush 7, the cartridge is
pushed toward
the needle 8 which pierces the seal and penetrates the cartridge, which at
this time
bears against the bush 7, as shown in figure 1. The contents of the cartridge
3 are then
emptied into the injection head through the needle 8 by applying axial thrust
to the
actuator rod 5 of the piston 4.
The filling means described in WO 95/24176 are suitable for an injection
head comprising a nozzle pierced with a single channel for discharging its
contents after
filling and through which the medication is forced to form a jet of medication
which
penetrates the skin of a patient by virtue of its momentum alone. The
injection head is
filled through this single channel, whose diameter is normally very small, for
example of
the order of a few hundred microns. Clearly this small diameter limits the
flowrate of the
medication into the injection head when filling it, which can take a long
time.
An injection head known in the art which uses no needle comprises, like the
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head 9 shown in figure 1 of the accompanying drawing, a tubular body 10
delimiting a
chamber 11 adapted to contain a volume of the medication and closed at one end
by a
transverse wall 12 through which pass microchannels 131, 132, etc parallel to
the axis X
of the injection head. The channels open onto an external face 14 of the head
9
designed to be applied to the skin of a patient to administer to the patient
the
medication contained in the chamber 11. The pain felt by the patient during
administration is reduced by distributing the medication in this way through a
plurality
of microchannels which have a small diameter, for example a diameter less than
200 wm.
The other end of the injection head 9 is closed by a piston 15 mobile inside
the chamber 11 along the axis X. A propulsion mechanism 16 which receives the
injection head 9 can suddenly drive the piston 15 toward the wall 12 of the
head,
thereby forcing the liquid contained in the head through the microchannels 13;
and
through the skin of a patient, to which the outside face of that wall is
applied. In this
case the filling device 1 is obviously separate from the injection head.
The means for filling a single microchannel injection head of the type
described in WO 95/24716 are not suitable for fast filling of a head with
multiple
microchannels of the type shown in figure 1 of the accompanying drawing.
The object of the present invention is precisely to provide a device for sub
cutaneous injection of a liquid medication without using a needle and
including means
for filling an injection head with said medication which does not have the
disadvantages
of the prior art devices and which in particular fills said head quickly.
The object of the invention, together with others that will become apparent
in the course of the following description, is achieved by a device for sub-
cutaneous
injection of a liquid medication without using a needle of the type described
in the
preamble of this description, which device is noteworthy in that the means for
filling the
head of the device comprise means for temporarily blocking at least one
microchannel
for injecting the medication and at least one passage through a wall of the
injection
head, adapted to cooperate with a cartridge of medication to allow the head to
be filled
with a volume of medication from the cartridge and equipped with check valve
means
for preventing said medication leaking out of said head through said passage.
As emerges in more detail later, the above passage can have dimensions
enabling the injection head to be filled quickly, in contrast to what happens
when the
head is filled through the microchannel(s) for injecting the medication under
the skin of
3 5 a patient.
Other features and advantages of the present invention will become
apparent on reading the following description and referring to the
accompanying
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drawing, in which:
figures 1 and lA show one embodiment of a device according to the
invention already described in part in the preamble of this description, and
figures 2, 2A and 3 show variants of the injection head of a device in
accordance with the invention.
Figure 1 of the accompanying drawing shows, assembled in a linear
arrangement along an axis X, a device 1 for filling an injection head 9 of an
injection
device in accordance with the invention mounted on the filler device and a
propulsion
mechanism 16 which is cocked manually and designed to actuate the injection
head 9
to administer medication contained in the head. It is clear that at the time
of actuation
the filler device 1 must be demounted from the head to enable its external
face 14 to be
applied to the skin of a patient, which is then opposite the outlets of the
microchannels
13;, which can also take the form of microslots. Similarly, the propulsion
mechanism 16
is not mounted on the head 9 when filling the head.
The propulsion mechanism 16 injects under the skin of a patient medication
previously loaded into the chamber 11 of the head 9 by the filling means in
accordance
with the present invention described in more detail later. The propulsion
mechanism
essentially comprises a cylindrical tubular body 17 in which slides a ram 18
spring-
loaded by a spring 19. Balls 201, 202, etc spring-loaded by springs 211, 21z,
etc in a
2 0 groove on the outside surface of the body 10 of the injection head 9 fix
the latter
removably to the propulsion mechanism 16. The ram 18 can be immobilized in a
top
position (as seen in figure 1), away from the head 9, by means that are not
shown.
Pressing a trigger button 23 releases the ram 18 which is propelled suddenly
by the
compressed spring 19 toward the piston 15 of the head 10 without compressing
the
intermediate volume of air 24 (which is not sealed) and drives the piston 15
of the head
9 at constant speed toward the end of the head. The medication contained in
the
chamber 11 then exits the chamber at constant pressure, in the form of a
spray, and
penetrates under the skin of a patient to which the surface 14 of the head is
applied, the
skin of the patient taking the place of the device shown in figure 1 for
filling the head.
The present invention is precisely concerned with new means for filling the
head 9 quickly with medication to be administered in spray form.
In a first embodiment of those means, shown in figure 1, the filler means
comprise means 25 for temporarily blocking the microchannels 13;, an axial
passage 26
through the center of the wall 12 of the injection head, and a housing 27
between the
ends of the passage 26 shaped to accommodate a tongue 28 of complementary
shape
(see figure lA).
The bush 7 mounted on the filling device 1 comprises an axial nozzle 29
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which projects from the end of the bush and through the passage 26 and opens
into the
chamber 11 of the head 9 when the latter is mounted on the bush to be filled
with
medication. To this end the needle 8 passes axially through the nozzle 29.
The microchannels of the head 9 are advantageously distributed
symmetrically about the axis of symmetry of the head. By way of illustrative
and non-
limiting example only, there can be two or more microchannels which can have a
diameter of 100 to 300 ~.m, in a ratio to the diameter of the chamber 11 of
1/20 to
1/100.
According to one feature of the injection head according to the invention, a
particular ratio is chosen between the diameter of the microchannels and the
diameter
of the cylindrical internal chamber 11 containing the liquid medication
solution to
guarantee the formation of a spray rather than a painful concentrated jet. The
ratio is
from 1/20 to 1/100 but must remain within the linear range of the propulsion
mechanism and preserve a small overall size of the injection head to guarantee
that it
can be manufactured in the traditional way. The liquid to be injected must
have a
kinematic viscosity less than 3 centistokes, given the increase in pressure at
the time
thrust is applied to the liquid by the piston 15.
Good results have been obtained with a chamber 11 with a diameter of
8 mm and microchannels with a diameter of 200 microns (0.2 mm), in which case
the
2 0 ratio is 8/0.2 = 40/1.
European patent EP 0 367 677 with the same applicant describes an
injection head in which the liquid to be expelled under pressure enters
oblique channels
at an angle to one another and opening onto a rounded concave surface,
producing
turbulence and additional head losses. In contrast to that practice, in
accordance with
the invention, and to prevent any head loss, it is necessary to pass directly
and without
intermediate diameters from the inside diameter of the cylindrical chamber to
that of
the microchannels.
According to the invention, the microchannels are no longer at an angle to
one another, must be perpendicular to the inside face of the chamber 11 and to
the
plane outside face 14 of the injection head which is in contact with the skin
of the
patient, and must be strictly parallel.
This feature is fundamental because it conditions the perfect regularity of
the resulting spray. Similarly, any defect in terms of perpendicularity would
be reflected
in poor diffusion against the skin of the patient and much of the sprayed
solution would
escape from the sides of the injection head applied to the skin. The injection
of the
whole of the prescribed dose and effective treatment of the patient by the
medication
would not be guaranteed.
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The microchannels have a length equal to 5 to 10 times their diameter to
prevent them bursting at the time of the injection and to prevent risk of
injury.
The microchannels must also be perfectly cylindrical to guarantee at their
outlet a perfect well aligned spray. This rules out fabrication techniques
such as some
5 laser beams (which act on the material in the manner of small torches),
because the
resulting holes would be irregular. Microdrilling is currently the most
reliable technique.
The head is then filled with a volume of medication in the following manner.
With the device 1 separated from the head, axial pressure is applied to the
operating
rod 5 of the piston 4 of the cartridge 3 of medication placed in the device 1
to bring the
seal 6 of the cartridge into contact with the needle 8, which then pierces the
seal, as
already explained. Axial movement of the cartridge 3 ends when the cartridge
abuts
against the bush 7. The medication fills the needle 8, expelling the air
previously
contained in it.
The head 9 is then fitted to the bush 7 of the filling device 1. To this end
the
bush 7 includes spring claws 301, 302, etc which engage an annular shoulder
farmed on
the injection head 9. The blocking means 25 are installed at the end of the
bush to
block the microchannels 131, 132 when the nozzle 29 passes through the passage
26.
Further movement of the piston 4 into the cartridge empties the latter into
the chamber
11 of the injection head 9. The piston 15 of the injection head moves from an
initial
position in which it bears on the end of the chamber, in contact with the
nozzle 29, to a
final position defined by the quantity of medication received. This procedure
ensures
that the chamber 11 contains only medication and not unwanted air. Because of
the
blocking means 25, the medication injected into the chamber 11 cannot escape
from it
via the microchannels 131, 132.
Clearly the quantity of medication injected into the chamber 11 can be
precisely varied by various means known in the art, for example by micrometer
adjustment of the travel of the piston 4 in the cartridge 3. The head 9 can
also be
transparent and graduated for this purpose.
With the head filled with a metered quantity of medication and the nozzle 29
removed from the passage 26, in accordance with the present invention, the
tongue 28
is inserted into the housing 27 to prevent the medication contained in the
chamber
escaping from it via the passage 26, which is now blocked by the tongue, which
thus
constitutes a check device. In the embodiment shown in figure 1 by way of
example
only, the wall 12 of the head 9 incorporates a transverse passage constituting
the
housing 27 and whose cross section in the plane of the drawing conforms to
that of the
tongue 28.
The head 9 can then be removed from the filling device 1 and installed on
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the propulsion mechanism 16.
If there is a risk of loss of medication by capillary action in the
microchannels 131, 132, the blocking means 25 remain at the outside ends of
the
microchannels. Those means can then take the form of a peel-off adhesive film
applied
to the face 14 of the injection head. In this case, the seal can be applied
before filling
the head. It is then removed just before administering the medication. The
presence of
this seal also satisfies hygiene requirements.
According to the invention, it is the diameter D of the injection needle 8
which limits the flowrate of the medication into the chamber 11 when it is
being filled,
not that of the very fine microchannels 131, 132, because the latter are not
used for
filling, in contrast to what is described in WO 95/24176. The diameter D can
then be
chosen so that filling can be carried out as quickly as required. For example,
the
diameter D can be in the order of 1 mm, whereas the diameter of the
microchannels
131, 132 is of the order of 100 to 300 wm.
It is now clear that the embodiment of the invention shown in figures 1, lA
achieves the stated object. Note, however, that using a removable tongue 28
which
must be installed in the head after filling it makes this embodiment somewhat
difficult
to use. Using a tongue of this kind can also give rise to sealing problems
during injection
of the medication, because of the high pressure in the chamber 11 at this
time.
Figures 2, 2A and 3 shown variants of the above embodiment adapted to
solve these problems. In these figures, reference numbers identical to those
used in
figure 1 correspond to identical or similar items or units.
In the figure 2 variant, the tongue 28 of the figure 1 embodiment is replaced
by a check valve 32, which is shown in more detail in figure 2A, Where it is
clear that the
valve comprises a central stem 33 and a transverse flexible skirt 34. The
central stem is
designed to be forced into the passage 26 with the skirt 34 pressed against an
inside
face of the end wall 12 of the injection head 9 by the pressure of the
medication
contained in the chamber 11. However, the skirt 34 is flexible and can be
lifted off that
inside face by the pressure of the liquid medication injected through the
nozzle 29
projecting axially from the end of the bush 7, to allow the medication to
enter the
chamber 11 when filling the head 9. To this end, the stem 33 carries splines
351, 352,
etc between which are formed spaces through which the medication passes around
the
stem 33. This arrangement is well known in the art for this type of valve.
Accordingly, the medication, pushed into the needle 8 in the direction of the
arrow F by device of the type shown in figure 1 can pass through the valve 32
into the
chamber 11. When the chamber 11 has been filled with a metered quantity of the
medication to be administered, the valve 32 prevents the medication flowing
out again
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through the central passage 26. The microchannels 131, 132 are blocked by
means 25
analogous to those described with reference to figure 2.
This variant accelerates filling and can facilitate automation of filling,
because it eliminates the operation of inserting the tongue 28 of the
embodiment shown
in figures l, lA, after filling the chamber 11. Also, the skilled person knows
how to
make skirt-type valves providing the required seal at the high pressures
encountered in
the chamber 11 of the head 9 during injection of the medication.
In the figure 3 variant, the valve 32, which is identical to that of the
figure 2
variant, is introduced into a passage 26' formed along the axis of the piston
15 instead
of in the end 12 of the head 7.
The nozzle 29 is modified so that it can hook onto the piston 15 during
filling. For this purpose it has a ring of spring claws 361, 362, etc adapted
to hook
removably into a groove in an annular housing 37 of the piston 15. In this
position, the
nozzle 29 can expel a volume of medication that enters the chamber 11 by a
mechanism analogous to that described with reference to figures 2, 2A. A
stopper 38
equipped with blocking means 25 is then applied to the face 14 of the head 9.
The figure 3 variant simplifies the structure of the wall of the head 9
because the arrangements needed to accommodate the check valve are transferred
to
the piston 15.
It is clear that the figure 1 embodiment, like the figure 2 and 3 variants,
enables either manual filling of the injection head with the medication just
before
administering the medication to a patient or automatic filling in the factory,
in which
case the heads are shipped ready for use. It is also clear that the figure 2
and 3 variants
are better suited to fast filling of the injection heads than the figure 1
embodiment, for
the reasons indicated above.
Of course, the invention is not limited to the embodiments described and
shown, which are described and shown by way of example only. Accordingly,
although
the invention has been described in its application to an injection head
including a
plurality of microchannels, it is obviously applicable to an injection head
including only
one medication injection microchannel. Equally, check valves other than those
described
above, for example ball valves, can be used. Thus a self-healing material
tongue can be
substituted for the tongue 28 shown in figure 1. In this case the tongue is
permanently
installed on the head, before filling the head. When the head is fitted to the
filling device,
a needle of the same type as the needle 8 pierces the self-healing tongue to
enable the
medication to flow into the head. On removing the head from the device, the
needle is
removed from the tongue, which "heals" itself automatically, preventing any
return flow
of the liquid. By shaping this tongue appropriately, the high pressure applied
by the
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medication to the scar in the tongue during administration of the medication
does not
re-open the scar, but instead closes it more strongly.
Equally, the cartridge can be replaced by a flask containing the liquid
medication or by any other form of packaging, the bush 7 being adapted
accordingly.
For automatic filling in the factory, an appropriate automated system
renders the operation repetitive at a high rate of throughput in order to
obtain injection
heads prefilled with a predetermined dose and shipped in sterile packaging.
It is also possible to check the volume of medication in the internal chamber
11 visually if the injection head 9 is transparent and graduated like a
syringe. This
simplifies filling it.
In a disposable version, the head can be made from a material that can be
injection molded. In a non-disposable version, the head can be made of steel
and
sterilized before use. The valve is still disposable and interchangeable in
this case.
According to another feature of the invention, in some applications, in
particular in the specific and particular field of vaccination, total
puncturing of the skin
is not required.
In this case, it is necessary to carry out a superficial injection into the
surface layer of the skin, like "scarification". To this end, it is sufficient
to replace the
microchannels 13; with microslots whose characteristics are within the
following
tolerances, depending on the product used and its kinematic viscosity, which
is again
less than 3 centistokes, as well as the required effect, the pressure again
being
constant. For example, a microslot can have a width from 10 w to 500 w, a
length from
100~to5000wandadepthfrom 100~.to5000w.
