Automatic injection device

The invention relates to an automatic injection device comprising an assembly of a discharge mechanism, a cartridge holder of synthetic material and a cartridge which is slidably accommodated in the cartridge holder. The cartridge includes a glass ampoule, if desired, enveloped by a sheath of shrinkable sheet, the ampoule consisting of an ampoule cylinder in which an injection liquid or various injection liquids separated from each other by stoppers and a piston which can be moved in the ampoule cylinder are provided. The assembly also includes a connection means for an injection needle in which or to which the injection needle, if desired, covered by a guard to maintain the needle in a sterile condition, is connected, and a shoulder between the ampoule cylinder and the needle connection means. The cartridge holder consists of a sleeve-like rear portion which is open at each end and which, after actuating the injection device, is traversed by the ampoule cylinder and the inner surface of which has substantially the same transverse dimensions over the whole length, and a front portion which forms one assembly with the sleeve-like portion and, after actuating the syringe, serves to discontinue the forward movement of the cartridge in the holder and to allow passage of the needle. The sleeve-like portion of the cartridge holder has a five-sided to fourteen-sided cross-section over a length which is at least equal to the length of the ampoule cylinder and is proportioned such that the ampoule cylinder engages the inner side surfaces of the sleeve-like portion with friction. The invention furthermore relates to a cartridge holder for the injection device.

The invention relates to an automatic injection device comprising an 
assembly of a discharge mechanism, a cartridge holder of a synthetic 
material and a cartridge which is slidably accomodated in the cartridge 
holder. The cartridge comprises a glass ampoule, which consists of an 
ampoule cylinder containing an injection liquid or various injection 
liquids separated from each other by stoppers and a piston which can be 
moved in the ampoule cylinder. The assembly further includes a connection 
means for an injection needle in which or to which the injection needle is 
connected, and a shoulder between the ampoule cylinder and the needle 
connection means. The cartridge holder consists of a sleeve-like rear 
portion, which is open at each end and which, after actuating the 
injection device, is traversed by the ampoule cylinder and the inner 
surface of which has substantially the same transverse dimensions over the 
whole length, and a front portion which forms one assembly with the 
sleeve-like portion and, after actuating the syringe, serves to 
discontinue the forward movement of the cartridge in the holder and to 
allow passage of the needle. 
Such an injection device, namely for one injection liquid, is known from 
British Patent Specification No. 1,528,735. The device disclosed in said 
Patent Specification moreover comprises a spacer element with which the 
contents of the ampoule can be reduced at will, and a needle guard of a 
flexible material which keeps the needle sterile during storage of the 
device. Such a needle guard is an excellent provision and is preferably 
used also in the syringe according to the present invention. 
An injector related to the injection device known from the above British 
Patent Specitication is described in U.S. Pat. No. 3,712,301. In the 
species shown in FIGS. 4 to 6 of this latter patent specification the 
cartridge holder is internally provided with three longitudinally 
extending ribs to distort the resilient sealing end portion of the ampoule 
during operation of the injector, thereby providing openings for flow of 
air in said end portion, and thus allowing the air locked in between the 
front of the cartridge holder and the front of the ampoule to escape 
backwards. 
An automatic injection device as mentioned in the opening paragraph in 
which various injection liquids separated from each other by stoppers are 
accommodated is disclosed in European Patent Application No. 72057 in the 
name of the Applicants. 
It has been found that when the injector known from the above British 
Patent Specification No. 1,528,735 or U.S. Pat. No. 3,712,301 is used, 
fracture of the glass ampoule often occurs, in particular when the ampoule 
is manufactured from unhardened glass. Upon actuating the device, 
apparently the material of the ampoule often cannot withstand the forces 
occuring upon relaxation of the spring forming part of the discharge 
mechanism. This disadvantage can be checked by using an ampoule around 
which a sheath of shrinkable plastic sheet has been shrunk, as described 
recently in European Patent Application No. 107874 also in the name of the 
Applicants. The injection device according to the present invention 
preferably comprises a glass ampoule enveloped by a sheath of shrinkable 
sheet. 
Automatic injection devices have been developed in particular for use by 
persons who have to administer an injection into their own body at a given 
instant which is not known beforehand. These persons include, for example, 
soldiers after having been exposed to a battle gas of the enemy, for 
example, a nerve gas. It should therefore be obvious that stringent 
requirements have to be imposed upon automatic injectors as regards their 
reliability. Such devices are usually stored for many years at a time and 
in addition are carried with the potential user for long periods of time 
under varying conditions. Despite these facts the reliability of the 
injector must remain sufficiently ensured at the critical instant when the 
injection is required. In fact, at said critical instant the user's life 
may depend on the ready operation of the injection device. 
Automatic injection devices are exposed to heavy shocks in particular when 
used by soldiers in the field. In order that in these circumstances the 
devices remain intact, i.e. still operate at the critical moment, high 
requirements must also be imposed upon the shock resistance of the 
injectors. It is therefore required, in particular by military authorities 
in various countries, that even extreme droptests do not adversely 
influence the ready operation of automatic injection devices. An example 
of a very extreme droptest is a test in which the automatic injector, 
without any further external protection means, falls from a height of 1.50 
m on a granite table. It has been found that thereafter approximately 15% 
of the automatic injectors no longer operated well even when the glass 
ampoule thereof was enveloped by a sheath of shrinkable sheet. 
It is the object of the present invention to provide an automatic injection 
device which maintains its ready operation also under the above-described 
extreme conditions. 
This object can be achieved by means of an automatic injection device of 
the type mentioned in the opening paragraph which, according to the 
invention, comprises a cartridge holder the sleeve-like portion of which, 
over a length which is at least equal to the length of the ampoule 
cylinder, has a five-sided to fourteen-sided cross-section and is 
proportioned such that the ampoule cylinder has a frictional engagement 
with the inner side surfaces of said sleeve-like portion. 
It has surprisingly been found that when such a cartridge holder is used, 
not only the shock resistance of the automatic injection device is 
improved such that an ampoule of unhardened glass may be used without any 
objection, but also that the subtle cooperation between the cartridge 
holder and ampoule is not adversely influenced. On the contrary, it has 
been found that upon actuating the injector according to the invention, 
the ampoule cylinder can move forward even smoother and better centred in 
the cartridge holder sleeve thus formed, while nevertheless the air in 
front of the ampoule can flow away backwards without any hindrance between 
the outer wall of the glass ampoule and the inner wall of the cartridge 
holder sleeve. Moreover, upon assembling the injection device according to 
the invention, positioning the cartridge in the cartridge holder is not 
hampered because of the flexibility of the plastic wall of the cartridge 
holder sleeve. The cartridge holder can be manufactured in a simple manner 
and hence cheaply, for example, by injection moulding, from a 
form-retaining slightly resilient synthetic material, for example, from 
polypropylene. 
It has furthermore been found in addition that the rigidity of the 
cartridge holder of the injection device according to the invention is 
greater than that of a known cartridge holder, as described, for example, 
in the above-mentioned British Patent Specification No. 1,528,735; of 
course, this applies to equal wall thicknesses of the cartridge holders. 
As a result of this, the bending resistance of the injection device is 
increased so that an extra contribution is provided to the reliability of 
the device. When used under extreme conditions, for example by soldiers in 
the field, the automatic injector may also be subjected to a large bending 
load, as a result of which the risk of fracture of the glass ampoule 
increases. Improvement of the bending resistance of the injection device 
hence is of great importance. 
It has been found that the advantages of the syringe according to the 
invention appear in particular when the sleeve-like part of the cartridge 
holder has a six-sided to twelve-sided cross-section. A cartridge holder 
sleeve having a seven-sided cross-section has proved to be extremely 
suitable. 
Without extra provisions on the inside of the cartridge holder sleeve, the 
possibility is not excluded that, when the injection device falls down on 
its front side or nose, the cartridge may slightly move forward in the 
cartridge holder sleeve. It may then occur that the needle emanates from 
the cartridge holder as a result of which the sterility of the needle is 
lost and, which is more serious, the tip of the needle is damaged. It has 
now been found that this risk can be avoided by providing at least three 
inner side surfaces of the sleeve-like portion of the cartridge holder of 
the injection device according to the invention with radially positioned 
raised portions which are distributed over the circumference of the 
sleeve-like portion and form one assembly therewith. During storage of the 
syringe these raised portions engage the ampoule shoulder or are 
positioned at a short distance in front of it. This provision which 
provides an extra contribution to the reliability of the injection device 
may be considered as a particular aspect of the invention because it can 
be used successfully only in a cartridge holder for an injection device 
according to the invention, i.e. a cartridge holder having a five-sided to 
fourteen-sided sleeve-like rear portion. As a matter of fact, the flat 
side walls in such a cartridge holder sleeve are so resilient that the 
raised portions thereon, provided their dimensions are suitable, can 
easily by pushed aside by the ampoule cylinder upon actuation of the 
syringe, so that the forward movement of the cartridge in the holder is 
not prevented or impeded in such manner that the injector no longer 
operates normally. On the other hand, the raised portions on the inner 
side surfaces of the cartridge holder sleeve are sufficient to prevent 
inadvertent movement of the ampoule within the holder, so to keep the 
cartridge in the cartridge holder in its place when the injector falls on 
its nose. Often all the inner side surfaces of the sleeve-like portion of 
the cartridge holder are provided with raised portions so that a 
seven-sided cartridge holder sleeve also comprises seven raised portions, 
but for the intended purpose fewer raised portions will suffice. 
The above provisions to improve the shock resistance of an automatic 
injection device are intended in particular for an automatic injector the 
ampoule of which is manufactured from unhardened glass. If the glass has 
been subjected to a special hardening, the risk of fracture upon falling 
or impacting of the injector generally is comparatively small. However, as 
stated in the European Patent Application No. 107874 mentioned 
hereinbefore such a hardening process is comparatively expensive and hence 
less attractive for automatic injectors which are manufactured in large 
quantities. 
The invention furthermore relates to a cartridge holder for the injection 
device described hereinbefore the sleeve-like portion of which has a 
five-sided to fourteen-sided cross-section over the whole or at least a 
part of its length.

The injector shown in FIG. 1 is in broad outline equal to that described 
and shown in the above-mentioned European Patent Application No. 107874. 
The embodiment shown in FIG. 1 is only one example of an automatic 
injection device in which the provisions for improving the shock 
resistance can be advantageously used. Other suitable examples of such 
injection devices are described and shown in European Patent Application 
No. 72057. 
The injector shown in FIG. 1 comprises an outer sleeve 1 having an inwardly 
bent edge 2 and circumferential groove 3, in which a cartridge assembly 4 
and a discharge mechanism 5 are accommodated. The cartridge assembly 
comprises a cartridge holder 6 which fits in the outer sleeve and at its 
front end has a circular aperture 7, and a cartridge 8 which is movable in 
the cartridge holder. The cartridge comprises an ampoule 9 consisting of 
an ampoule cylinder 27, a neck 28, and a shoulder 29 between cylinder and 
neck. An injection needle 13 comprising a rubber needle guard 12 is 
connected on the neck of the ampoule by means of a needle holder 14. An 
injection liquid 10 is present in the ampoule between a piston 11 movable 
in the ampoule cylinder and a membrane 15 provided between the neck of the 
ampoule and the needle holder. Said membrane keeps the injection liquid 
separated from the needle during storage of the injector, but bursts open 
during use of the syringe so that the injection liquid can reach the 
needle cannula. Furthermore, a spacer element 16 is provided behind the 
piston with which the volume of the ampoule for the injection liquid is 
reduced. 
As the injector described in British Patent Specification No. 1,528,735, 
the discharge mechanism comprises an outer gun sleeve 17 locked in groove 
3 of outer sleeve 1 and an inner gun sleeve 18 slidably accomodated in the 
outer gun sleeve and comprising a coil spring 19 as a power source. The 
coil spring fits around a plunger 20 with a sufficient amount of play, the 
plunger consisting of a plunger head which is inserted in the spacer 
element, a central portion 12 and an end portion 23. The end portion 
consists of four resilient prongs the conical ends 24 of which bear on a 
metal sealing ring 25 around an aperture in the rear face of the inner gun 
sleeve. In the FIG. 1 syringe the safety member consisting of a cap with a 
safety pin which may extend between the prongs of the plunger, has already 
been removed so that the syringe is ready for use. A sheath 26 of PVC 
shrinkable sheet is shrunk around the whole ampoule, including its neck 
and rear edge. 
For further explanation, FIG. 2 shows the cartridge holder 6 of FIG. 1 on 
an enlarged scale. The cartridge holder consists of a tapering nose 
portion 30 which on its front comprises longitudinal ribs 31 for centering 
the needle guard 12. A circular aperture 7 is recessed in the front face 
of nose portion 30. The nose portion adjoins a sleeve-like rear portion 32 
having increased transverse dimensions which are equal or substantially 
equal over the whole length. The shoulder 33 formed between the nose 
portion and the sleeve-like portion forms an abutment for the ampoule 
shoulder 29 in the position in which the cartridge is maximally moved 
forwards in the cartridge holder. As is shown clearly in the 
cross-sectional view of FIG. 4, the sleeve-like rear portion of the 
cartridge holder has a seven-sided cross-section. 
In the cross-sectional view of the cartridge holder shown in FIG. 4 and 
viewed in the direction of the nose portion, the shoulder 33 formed by the 
nose portion of reduced diameter, the centering ribs 31 and the aperture 
in the front face of the nose portion are also shown. Seven radially 
positioned raised portions 34 which form one assembly with the cartridge 
holder wall are provided on the inner side surfaces of the sleeve-like 
rear portion of the cartridge holder. As is shown in FIG. 1, said raised 
portions constitute an abutment for the ampoule shoulder 29; upon 
actuating the injector, however, the ampoule can easily be moved forwards, 
the raised portions positioned on the resilient side walls of the 
sleeve-like portion of the cartridge holder being pushed aside without any 
difficulty (overridden). 
For further explanation, FIG. 5 shows on an enlarged scale a detail of a 
wall part of the cartridge holder sleeve with two raised portions. FIG. 3 
furthermore shows on an enlarged scale a detail of a longitudinal 
sectional view of the cartridge holder wall taken on the line III--III of 
FIG. 2. In FIG. 3, i denotes an inner side surface and o denotes an outer 
side surface. FIG. 6 finally is a cross-sectional view which is comparable 
to that of FIG. 4, but this time through a cartridge holder having a 
twelve-sided rear portion. The reference numerals correspond to those of 
FIG. 4. 
The use of the injection device according to the invention is the same as 
that of the one described in British Patent Specification No. 1,528,735 
mentioned hereinbefore and needs no further explanation. 
Injection devices according to the invention in which the ampoule had been 
manufactured from unhardened glass around which a sheath of shrinkable 
sheet had been shrunk according to the above-mentioned European Patent 
Application No. 107874 and which had been provided with a cartridge holder 
having a seven-sided sleeve portion as described hereinbefore, were 
compared with identical injectors comprising a cartridge holder having a 
cylindrical sleeve portion internally provided with three longitudinal 
ribs (as described in the above U.S. Pat. No. 3,712,301). The cartridge 
holders had been manufactured from polypropylene by injection moulding. 
The injectors to be tested were subjected to a droptest, either by 
dropping them flat on a granite table from a height of 1.50 meters 
(droptest A), or by dropping them six successive times from a height of 
1.20 meters on a concrete floor (droptest B). The injectors were then 
"discharged". The following results were obtained: 
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injector 
cartridge number of 
holder glass tested well expelled 
sleeve ampoule droptest injectors 
number % 
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seven-sided 
unhardened 
A 50 49 98 
seven-sided 
" B 50 50 100 
cylindrical 
" A 50 43 86 
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"Well expelled" is to be understood to mean that upon "discharge" of the 
injector, the injection liquid has left the injector through the injection 
needle and has not prematurely leaked away from the ampoule due to 
fracture thereof. 
From the above results it appears that when a cartridge holder sleeve 
having a plurality of flat sides is used instead of a cylindrical one, the 
percentage of fracture of the ampoules in droptests of automatic injection 
devices can be reduced to an acceptable percentage.