Automatic injector

The invention relates to an automatic injector for injecting one or more injection liquids, comprising an assembly of a discharge mechanism, a cartridge in a cartridge holder, and an outer sleeve which is telescopically slidable around the cartridge holder, which cartridge comprises a barrel, in the barrel a piston and a number of separating stoppers equal to one less than the number of injection liquids, a needle holder with injection needle and optionally a by-pass for injection liquid. The injector is suitable for accommodating a solid and a solvent therefor, and for that purpose comprises a passable stopper between solid and solvent and a solvent by-pass in the barrel wall or in the passable stopper, in which, by a single or repeated operation of telescoping external parts of the injector solvent can pass the passable stopper and can reach the solid, as a result of which the injector can be made ready for use.

The invention relates to an automatic injector for injecting one or more 
injection liquids, in which, prior to use, different substances which are 
not allowed to be in contact with each other for a long period of time can 
be stored separately, comprising an assembly of a discharge mechanism, a 
cartridge in a cartidge holder, and an outer sleeve which is 
telescopically slidable around the cartridge holder, the cartridge 
comprising: 
a hollow, substantially cylindrical barrel which is open at its rear end; 
a piston which is movable in the barrel and seals same, 
a number of separating stoppers equal to one less than the number of 
injection liquids, said separating stoppers being movable in the barrel 
and having circumferences that adjoin the inner wall of the barrel in a 
sealing manner, thereby keeping the injection liquids in the barrel 
separated from each other prior to use of the injector, 
a needle holder connected to the front end of the barrel in a sealing 
manner and comprising a neck for sealingly gripping a needle, which 
needle, if desired, is covered by a sheath to maintain said needle in a 
sterile condition, and 
in case the injector is destined for at least two injection liquids, a 
by-pass for injection liquid in front of said separating stopper or front 
separating stopper, for permitting said injection liquid or liquids behind 
the stopper or stoppers to reach the injection needle, when during use of 
this injector the stopper or stoppers is or are moved forward, said 
by-pass extending in the longitudinal direction over a distance slightly 
larger than that of the separating stopper or collection of separating 
stoppers, so that said stopper or collection of stoppers in their ultimate 
forward position does or do not cover the rear end of said by-pass. 
Such a injector in known from the U.S. Pat. Nos. 4,529,403 and 4,394,863. 
The injection needle of the injectors disclosed in said patent 
specifications comprises a needle guard of a resilient material which 
keeps the needle in a sterile condition during storage of the injectors 
and, when the injectors are used, serves as a shock absorber for the 
cartridge. Such a needle-guard is an excellent provision and is preferably 
also used in the injector according to the present invention. 
Automatic injectors have been designed in particular for use by human 
beings who at a given instant, which is not known beforehand, have to 
administer an injection into their own body. These beings include, for 
example, soldiers after having been exposed to an enemy's battle gas, for 
example, a nerve gas. It therefore will be obvious that automatic 
injectors must satisfy stringent requirements regarding their reliability 
in use. Such injectors are usually stored for many years at a time and in 
addition, after having been handed over to the potential users, will be 
kept by said users for long periods of time under varying conditions; the 
proper operation of the injectors must be sufficiently ensured. In fact, 
at the critical instant the user's life may depend on the operation of the 
injector. Therefore, automatic injectors must satisfy stringent 
requirements as for their storage stability. 
The administration of several medicaments or antidotes is often necessary 
in particular for military use, inter alia, because, of course, nature and 
composition of the battle gas used by the enemy are not known beforehand 
and/or to achieve an effective therapy. Some medicaments, which are 
sufficient storage-stable as solids, are not stable for the required long 
storage period after having been dissolved in a solvent to form a solution 
suitable for injection. An injector in which a solid as such can be 
accommodated might provide a solution to the problem of storing these 
medicaments. It is remarkable that such an automatic injector has, so far 
as known, not yet been realised. Obviously, the technical problems 
occuring in developing such an injector have so far been prohibitive. 
The present invention provides a solution to the above problem, starting 
from the recognition that the instability of such medicament solutions is 
always relative, i.e. that such substances always have a certain, albeit 
restricted, stability in solution. It has now been found that an injector 
can be used for the separate storage of at least two different substances 
which may not be in contact with each other for a long period of time, in 
which one of the substances in the injector is solid and can be injected 
as an injection liquid only after dissolving in a solvent, if by a simple 
operation prior to the actual use the injector is made ready for use. This 
operation of making the injector ready for use may take place a shorter or 
longer time before the use of the injector, depending on the stability of 
the medicament solution, either by the potential user himself, or by the 
person who hands over the injector to the user. In order to minimise the 
possibility of mistakes, it is recommendable to make the injectors ready 
for use immediately before or upon providing the injectors to the 
potential users, for example, soldiers in the field. This is advisable in 
all those cases in which the medicaments or antidotes in solution are 
sufficiently stable for a period of at least a few hours a day. Making the 
injector ready for use is a simple operation, namely performing once or 
repeatedly a simple telescoping movement of external parts of the injector 
with respect to each other, which operation can easily be carried out. 
In order to be able to use an injector of the type mentioned in the opening 
paragraph for the separate storage of at least two different substances 
one of which is solid and can be injected as an injection liquid only 
after dissolving in a solvent, in which at the same time the advantages 
known from the U.S. Pat. No. 4,529,403 mentioned hereinbefore, e.g. easy 
handlability, rapidly ready for use, and relatively uncomplicated which is 
in favour of the reliability, have been maintained, the injector according 
to the invention is designed in such a way, 
that the discharge mechanism is in operative relationship with the piston 
via a plunger and is capable of telescoping movement relative to the 
cartridge holder, permitting the injector to be made ready for use by a 
single or repeated forward movement of the piston in the barrel, 
that prior to using the injector, the cartridge at its front end is 
provided with a sealing means to prevent injection liquid from leaving the 
injector via the needle during making the injector ready for use, 
that a passable stopper, movably provided in the barrel in front of the 
piston and which, prior to making the injector ready for use, adjoins the 
inner wall of the barrel in a circumferentially sealing manner and keeps 
the solid separated from the solvent, and 
that a solvent by-pass for liquid is situated in the barrel wall over a 
length slightly exceeding the length of the passable stopper, or in the 
passable stopper, said solvent by-pass permitting the solvent to pass the 
passable stopper and reach the solid in front of said stopper and dissolve 
same upon making the injector ready for use. 
The injector according to invention is particularly flexible, because any 
desired number of injection liquids can be injected therewith dependent on 
the chosen number of separating stoppers and on the length of the by-pass 
for injection liquid. For practical considerations it is desirable to 
restrict the number of injection liquids to at most four. 
The solid may be present in the form of an, optionally lyophilized, powder, 
a tablet, granules, crystals, pills, and the like. The term "solid" should 
be interpreted widely and also includes a medicament which can be injected 
only afters dilution with a diluent. Such medicaments may be accommodated 
in the injector in the form of pastes or concentrated solutions which 
cannot be injected as such. The solvent by-pass then serves as a by-pass 
for the diluent. The terms "solid" and "solvent" for the said solid, as 
used in the specification and claims, should therefore be understood to 
include "medicament to be diluted before injection" and "diluent" for such 
a medicament. 
If, in addition to a solid and a solvent therefor, the injector comprises 
one or more injection liquids, these may be situated in front of a or 
behind the compartments comprising solid and solvent. In the former case, 
which is to be preferred for practical reasons, the solid is enclosed 
between the passable stopper and the separating stopper or the rear 
separating stopper, and the solvent for the solid between the piston and 
the passable stopper. In the latter case the solvent for the solid is 
enclosed between a separating stopper and the passable stopper, injection 
liquid being accommodated in the injector behind said separating stopper. 
Due to the simplicity of the operation for making ready for use, the 
injector according to the invention is also particularly suitable for 
packaging in a multi-unit pack, for example, a multi-unit box, in which, 
when the injectors are handed over to the potential users, the injectors 
can be made ready for use collectively, for example, by performing a 
single or repeated telescoping movement of a wall of the box. 
The following explanation serves to elucidate the operation of making the 
injector according to the invention ready for use. As a result of the 
inward telescoping movement of the discharge mechanism relative to the 
cartridge holder the piston in the barrel is moved forward. The pressure 
exerted on the piston propagates to the passable stopper via the liquid or 
liquids between piston and passable stopper. Therefore, said passable 
stopper is moved forward over the same distance as the piston until its 
rear face is present beyond the rear end of the solvent by-pass. Because 
the cartridge is sealed at its front end, pressure is built up in the 
barrel under the influence of which the solvent behind the passable 
stopper passes said stopper via the by-pass. When the force exerted to 
move the discharge mechanism relative to the cartridge holder is removed, 
the pressure built up in the barrel provides the piston resuming its 
initial position, the passable stopper remaining in its place so that, 
under the influence of the same pressure, air from the space in front of 
the solvent by-pass (the compartment for solid) flows backwards through 
the by-pass. Dependent on the relative dimensions of the compartment for 
solid and the room destined for the solvent respectively, a smaller or 
larger portion of the solvent has reached the solid in the compartment for 
solid. This operation may be repeated ("pumping") until sufficient solvent 
has been added to enable the solid to dissolve to an injection liquid. 
During this pumping operation, the injector should be kept with its front 
or its nose downward so as to ensure the transfer of the solvent via the 
by-pass to the compartment for solid. With the usual relative dimensions 
of the rooms necessary to accommodate solid and solvent, approximately 
five times "pumping" is usually sufficient to transfer so much solvent to 
the compartment for solid that a solution is obtained which is suitable 
for injection. The injector is now ready for use and can be applied by the 
user at any desired moment to administer an injection. 
In order to be able to perform the above operation of making the injector 
ready for use it is essential for the cartridge to be sealed at its front 
end. Otherwise, injection liquid would leak away and leave the injector 
via the needle as a result of the pressure build-up in the barrel during 
making the injector ready for use. The barrel may comprise at its front 
end a sealing stopper or membrane which keeps the barrel closed during 
making the injector ready for use, but which bursts open or is pierced 
upon using the injector, thus uncovering the passage for the injection 
liquid or liquids so that it/they can leave the injector and be injected. 
However, the injector according to the invention is preferably constructed 
in such a way that the injection needle prior to use of the injector is 
covered by a sleeve-like needle guard of a resilient material which is 
connected with its open end around the neck of the needle holder and which 
in the proximity of its closed end keeps the front end portion of the 
needle tightly enclosed. This is to be understood to also include that 
situation in which the tip of the needle has been inserted into the rubber 
of the closed end of the needle guard to such an extent that the needle 
opening is sealed completely by the rubber. The object of such a needle 
guard hence is twofold, namely keeping the injection needle in a sterile 
condition before use of the injector and sealing the cartridge at its 
front end. When using the injector, the closed end of the needle guard is 
pierced by the tip of the needle, after which the injection liquid or 
liquids can leave the injector via the injection needle as described in 
U.S. Pat. No. 4,529,403 mentioned hereinbefore. 
The by-pass for injection liquid in front of the separating stopper or 
front separating stopper may be provided in the barrel and, dependent on 
the material from which the barrel is manufactured, may be constructed in 
various manners as will be described hereinafter for the solvent by-pass. 
A glass barrel is usually preferred in which in a favourable embodiment 
the by-pass comprises at least one outwardly projecting bulge of the 
barrel wall extending in the logitudinal direction of the barrel. In an 
equally favourable embodiment the by-pass for injection liquid comprises 
at least one radially inwardly directed ridge on the inner wall of the 
barrel or a separate plastics fitting mounted within the wall of the 
barrel, said ridge or fitting extending in the longitudinal direction of 
the barrel and having a length slightly exceeding the length of the 
separating stopper or collection of separating stoppers, so that upon use 
of the injector said stopper or stoppers is or are deformed by contact 
with said ridge or fitting, a passage for the injection liquid or liquids 
behind said stopper or stoppers being formed allowing said liquid or 
liquids to pass said stopper or stoppers. Of course, various other 
embodiments of the by-pass are possible without departing from the scope 
of the present invention. 
In a preferred embodiment the injector according to the invention is 
constructed in such a way that the injection needle is connected to the 
barrel by means of a needle holder which comprises a collar sealingly 
connecting the needle holder to the front end of the barrel and keeping 
the barrel in radially spaced relationship from the cartridge holder. As a 
result of this, also when using one or more outwardly projecting bulges of 
the barrel wall as a by-pass for injection liquid and/or solvent, the 
inner surface of the cartridge holder can remain rotationally symmetric. 
The cartridge holder thus need not comprise a recess or recesses to be 
able to accommodate therein such a bulge or such bulges of the barrel 
wall. As a result of this the assembly is facilitated considerably while, 
when using the injector as described in U.S. Pat. No. 4,529,403 mentioned 
hereinbefore, the cartridge can more easily move forward in the holder. 
The injector in this latter embodiment is preferably constructed in such a 
way that the injection needle is connected to the barrel by means of a 
needle holder, comprising a collar with which the needle holder is 
sealingly connected to the front end of the barrel, a neck in which the 
injection needle is connected, a hollow, substantially cylindrical shaft 
between collar and neck, and a by-pass for injection liquid in the wall of 
the shaft allowing the injection liquid or liquids behind the separating 
stopper or stoppers to reach the injection needle when during use of the 
injector the stopper or stoppers is or are moved forward into the shaft of 
the needle holder. For technical reasons of production a by-pass for 
injection liquid provided in the wall of the needle holder is to be 
preferred to a by-pass in the barrel wall because such a needle holder 
having a by-pass can be manufactured simply, preferably by injection 
moulding, from a suitable synthetic material. For example, the by-pass for 
injection liquid in the wall of the shaft of the needle holder may be 
formed in a suitable manner as shown and described in U.S. Pat. No. 
4,529,403 mentioned hereinbefore. In such a construction, said by-pass 
comprises at least one slot recessed in the inner wall of the shaft and 
extending in the longitudinal direction of the shaft from the rear end of 
the shaft and communicating with the open rear end of the injection needle 
via at least one slot radially recessed in the rear face of the neck of 
the needle holder. In another likewise suitable embodiment the inner wall 
of the shaft of the needle holder comprises at least one ridge which 
extends from the rear end of the shaft in the longitudinal direction of 
the shaft so that when using the injector the separating stopper or 
stoppers is or are deformed by contact with the said ridge, a passage for 
injection liquid behind the said stopper or stoppers being formed 
permitting said liquid to pass the stopper or stoppers, the rear face of 
the neck of the needle holder or the front face of the separating stopper 
or front separating stopper comprising a plurality of spacing supports 
allowing said liquid, after passing the stopper or stoppers, to reach the 
open rear end of the injection needle. When the rear face of the neck of 
the needle holder comprises spacing supports for passing the injection 
liquid, said spacing supports may be constructed as ridges provided 
radially on said rear face as an extension of the ridges on the inner wall 
of the shaft. 
It is advantageous for the injector to comprise means to prevent a forward 
movement of the cartridge in the cartridge holder during making the 
injector ready for use. Otherwise the possibility might exist that during 
making the injector ready for use the barrel with the needle connected 
thereto might move forward into the cartridge holder, as a result of which 
the needle tip might emanate forward from the injector. Suitable means to 
prevent this are, for example, a plurality of radially provided cams or a 
circumferential edge on the inner wall of the cartridge holder which keeps 
the cartridge locked against a forward movement in the cartridge holder 
during making the injector ready for use, but which easily allows passage 
of the cartridge upon the actual use of the injector. 
It is of essential importance that the injector can easily be made ready 
for use by a suitable choice of the mutually telescopically slidable 
external parts of the injector. In a preferred embodiment the injector 
according to the invention is constructed in such a way that the discharge 
mechanism can be moved telescopically relative to the outer sleeve 
comprising the cartridge holder locked therein against forward movement, 
so that by a single or repeated operation of inwardly telescoping the 
discharge mechanism relative to the outer sleeve, as a result of which the 
piston is moved forward in the barrel, the injector is made ready for use. 
In another, likewise suitable, embodiment the injector is constructed in 
such a way that the cartridge holder is telescopically movable relative to 
the outer sleeve comprising the discharge mechanism locked therein against 
rearward movement, so that by a single or repeated operation of inwardly 
telescoping the cartridge holder relative to the outer sleeve, as a result 
of which the piston is moved forward in the barrel, the injector is made 
ready for use. The discharge mechanism usually comprises a power source, 
for example a coil spring, which upon use of the injector can move the 
cartridge from a inoperative to an operative condition, locking means to 
control the actuation of the power source, and safety device to block said 
locking means. The telescopic movement mentioned hereinbefore of or 
relative to the discharge mechanism is to be understood to means also a 
movement of a relative to a component of the discharge mechanism, for 
example, the safety device. 
It is advantageous, prior to making the injector ready for use, to fix the 
mutually telescopically slidable external parts of the injector, i.e. the 
discharge mechanism or the cartridge holder relative to the outer sleeve, 
by means of a detachable locking member for prevenging unintentional 
movement of said parts relative to each other. In the first-mentioned 
preferred embodiment a locking ring or locking clip may be used for this 
purpose which serves to fix the distance between the discharge mechanism 
and the outer sleeve and which can easily be detached to allow making the 
injector ready for use. 
If desired, the injector may comprise an indication that the injector is 
ready for use, so that the user can easily ascertain that the operation of 
making the injector ready for use has been carried out. In case a 
detachable locking member is used, a good indication is, for example, the 
provision of conspicuous colour (signal colour) on the locking member or 
on that portion of the injector which prior to making the injector ready 
for use is covered by the locking member. 
Moreover it is favourable to fix the distance over which the external parts 
of the injector have to be telescoped relative to each other upon making 
the injector ready for use, the so-called "pumping stroke". In the 
embodiment in which a detachable locking member is used to fix the 
distance between the mutually telescopic parts relative to each other 
before the injector is made ready for use, said "pumping stroke" may be 
provided to correspond to the distance fixed by the locking member. Of 
course there are various other possibilities to fix the "pumping stroke". 
It will be obvious that various components of the injector according to 
the invention, for example, the outer sleeve, the cartridge holder and 
parts of the discharge mechanism, are preferably manufacatured from a 
form-retaining, slightly resilient synthetic material, for example, by 
injection moulding. It is advantageous to construct the cartridge holder 
in such a manner that the portion covering the barrel has a five-sided to 
fourteen-sided cross-section as described in Netherlands Patent 
Application No. 8403326; as a result of this the shock resistance of the 
injector is improved. 
The solvent by-pass may be provided in the barrel wall or in the passable 
stopper. In the latter case the passable stopper may comprise a non-return 
valve, permitting passage of liquid under the influence of a certain 
pressure exerted in one direction, but sealed when the direction of the 
pressure is reversed. Such a non-return valve is disclosed, for instance, 
in the German utility model (Gebrauchsmuster) No. G 8603917.2. When using 
a solvent by-pass in the barrel wall this solvent by-pass may be 
constructed in various manners. The barrel may be made of glass or a 
suitable synthetic material; in the latter case the barrel may be 
manufactured, for example, by injection moulding. When the barrel is of 
synthetic material, the by-pass in the barrel wall preferably comprises at 
least one slot recessed in the inner wall of the barrel and extending in 
the longitudinal direction of the barrel over a length slightly exceeding 
the length of the passable stopper. In another preferred embodiment the 
inner wall of the barrel comprises, at the area of the by-pass, at least 
one ridge which extends in the longitudinal direction of the barrel over a 
length which slightly exceeds the length of the passable stopper so that, 
when the injector is made ready for use, said stopper is deformed by 
contact with the ridge or ridges, a passage for the solvent behind said 
passable stopper being formed allowing said liquid to pass the stopper. 
Similar by-passes can also be provided in a glass barrel wall, but 
synthetic materials are better suitable for this purpose. A glass barrel 
is by far to be preferred to a barrel of a synthetic material because 
synthetic materials generally are less suitable than glass to store 
therein for a long period of time liquids intended to be injected; 
synthetic materials may contaminate the liquids or may adversely influence 
the stability of the said liquids. However, glass has for its disadvantage 
that it is fragile. The use of a sleeve of a shrinkable plastic sheet 
which is shrunk around the glass barrel, as disclosed in European Patent 
Application No. 107874, in particular as shown in FIG. 4 thereof, 
considerably improves the breaking strength of barrels of unhardened 
glass. The wall of a glass barrel can most simply be provided with a 
by-pass by deforming the wall of the barrel at the area of the by-pass 
over a length slightly exceeding the length of the passable stopper, so 
that, when the injector is made ready for use, the solvent behind this 
stopper can pass the stopper at the area of the deformation. The local 
deformation of the barrel wall preferably comprises at least on outwardly 
projecting longitudinal bulge of the barrel wall through which, when the 
injector is made ready for use, the solvent behind the passable stopper 
can reach the solid in front of this stopper, or comprises at least one 
inwardly projecting longitudinal ridge of the barrel wall as a result of 
which, when the injector is made ready for use, the passable stopper is 
deformed by contact with the ridge or ridges, a passage for the solvent 
behind the passable stopper being formed through which said liquid can 
reach the solid in front of said stopper past the stopper. The barrel wall 
may alternatively be deformed locally in such a manner that the barrel 
wall at that area has an oval cross-section, so that, when the injector is 
made ready for use, the solvent behind the passable stopper can reach the 
solid in front of said stopper. 
A local deformation of the wall of the barrel in the form of one or more 
outwardly projecting longitudinal bulges is generally considered to be the 
best suitable solution for a by-pass in the glass barrel wall, because 
this can be provided very simply in a barrel wall and during operation of 
the injector constitutes a reliable passage for the solvent. When a 
collared needle holder is used, this ensures, together with the preferably 
used clamping sleeve to be described hereinafter and connected in a 
clamping manner around the rear end of the barrel, that such a bulge or 
such bulges in the glass barrel wall is or are protected from damage or 
fracture upon assembling the injector. By using a collared needle holder 
and a clamping sleeve, it is moreover not necessary to adapt the shape of 
the cartridge holder to the shape of the outwardly bent by-pass in the 
barrel, and the assembling, in particular the automatic assembling, of the 
cartridge in the holder is not impeded by the asymmetric cross-section of 
the barrel at the area of the by-pass.

The injector shown in FIG. 1 is constructed for the greater part as 
described in U.S. Pat. No. 4,529,403 mentioned hereinbefore. In outline, 
the injector comprises a cylindrical outer sleeve 11 in which a cartridge 
holder 13 is rearwards movably provided, in which holder a cartridge 12 is 
accommodated, comprising a barrel 14, a piston 15 in one end of the barrel 
and a needle holder 16 at the other end. At the front end of the barrel 
the needle holder is connected by means of a collar 18. The needle holder 
further comprises a neck 20 in which an injection needle is connected, and 
a shaft 19 between collar and neck. The needle is covered in a sterile 
manner by a sleeve-like needle guard 21 of rubber. The closed end portion 
38 of the rubber needle guard is narrowed internally and in this manner 
keeps the front end portion of the needle tightly enclosed. The front end 
portion of the needle guard may also be constructed so as to be solid, the 
tip of the needle being pierced into the solid rubber of the guard over 
such a distance that the needle aperture is fully sealed. Four 
longitudinal slots 22 are recessed in the side wall of the shaft 19 of the 
needle holder and adjoin slots 35 which are radially recessed in the rear 
face of the neck and which in their turn communicate with the open rear 
end of the injection needle. In the tapering nose portion 39 of the 
cartridge holder 13 a central aperture 24 is recessed. A clamping sleeve 
23 which, like the collar 18 of the needle holder, is movable in the 
cartridge holder 13, is connected in clamping manner around the rear end 
of the barrel 14 by means of snap joint. The cartridge 12 is accommodated 
in the cartridge holder 13 in such a manner that the closed end of the 
sleeve-like needle guard 21 engages the end of the tapering nose portion 
39 of the cartridge holder. A plurality of longitudinal ribs 40 in said 
nose portion ensure the rigidity and the centering of the needle with 
needle guard. In order to prevent any unintentional forward movement of 
the barrel with needle holder in the cartridge holder during making the 
injector ready for use, the inner wall of the cartridge holder 13 
comprises a number of radially extending inward projections 50 which 
engage the outwardly projecting front end of the collar 18 of the needle 
holder. The outer sleeve 11 has such a length that the cartridge holder 13 
with cartridge 12 is accommodated in the front part and the discharge 
mechanism 25 in the rear part. The discharge mechanism comprises an inner 
piston sleeve 41 having an outwardly bent flange at the front end which is 
spaced from the rear edge of the cartridge holder with clamping sleeve 23. 
The coiled spring 26 is locked within said inner pistol sleeve by means of 
a plunger 27 as described in British Patent Specification No. 1,449,986 
mentioned hereinbefore. An outer pistol sleeve 42 is provided around the 
inner pistol sleeve so as to be slidable and is locked in the outer sleeve 
11 against rearward movement by means of a radially outwards extending 
circumferential edge 43 engaging in a circumferential groove 49 in the 
inner wall of the outer sleeve. Said circumferential groove 49 extends 
forward in the wall of the outer sleeve over a distance which is 
considerably larger than the width of the circumferential edge 43 on the 
outer wall of the outer pistol sleeve. A safety device 28 the safety pin 
45 of which extends between four resilient prongs 46 at the rear end of 
the plunger and in this manner protects the injector against unintentional 
actuation, comprises a cap 44 which engages the inwardly bent end of the 
outer pistol sleeve 42. The barrel 14 is divided into four separated 
compartments by two separating stoppers 32 and 30 and by a passable 
stopper 31, namely liquid compartments 29 and 36 which comprise injection 
liquids, a compartment 33 for the solid, and a compartment 37 for the 
solvent for said solid. The stoppers and the piston are provided in the 
barrel so as to be movable and sealing circumferentially on the inner wall 
and are manufactured from a slightly flexible material, preferably from a 
rubber of a pharmaceutical quality. The shaft 19 of the needle holder 16 
is proportioned in such a way that the space 29 bounded by the rear face 
of the neck and the side wall of the shaft, apart from the slots in the 
shaft, has approximately the same or a slightly larger diameter than the 
inner wall of the barrel 14 and is slightly longer than the collective 
separating stoppers 30 and 32, so that said space 29 can be filled 
substantially entirely by the collective separating stoppers in their 
ultimate forward position; however, the ends 34 of the slots 22 adjoining 
the barrel remain uncovered. As stated, the solid is accommodated in 
compartment 33 between the rear separating stopper 30 and the passable 
stopper 31, and the solvent for the solid is accommodated in compartment 
37 between the piston 15 and the passable stopper. The barrel 14 comprises 
a by-pass for solvent 47 in the form of a longitudinal bulge, more clearly 
visible in the cross-sectional view of FIG. 2. A locking clip 48 keeps the 
distance a between the front edge of the cap 44 of the safety device and 
the rear edge of the outer sleeve 11 fixed before the injector is made 
ready for use. 
The injector shown in FIG. 1 is made ready for use by moving the discharge 
mechanism, after having removed the locking clip 48, forward over a 
distance a by means of the cap of the safety device; when the pressure on 
the cap is removed, the discharge mechanism is returned to its original 
position by the pressure built up in the injector. When the cap has been 
moved forward over the distance a, the pumping stroke, until the front 
edge of cap 44 engages the rear edge of the outer sleeve 11, the piston 15 
and the passable stopper 31 have moved forward in the barrel. The rear end 
of the by-pass for solvent 47 has become accessible for the solvent in 
compartment 37, so that a quantity of solvent can flow to the solid in 
compartment 33. This situation is shown in FIG. 3. When the pressure on 
the cap 44 is removed, the piston 15 moves back again, approximately to 
its original position, under the influence of the compressed air in 
compartment 37. After "pumping" has been repeated approximately four 
times, in which the injector is held with its nose directed downwards, 
sufficient solvent has been added to the solid in compartment 33 to enable 
the solid to be dissolved sufficiently. A solution of the solid is now 
present in compartments 33 and 37 and may be used as an injection liquid. 
This situation is shown in FIG. 4, the injector being now ready for use. 
The injector which has been made ready for use may then be carried by the 
potential user and be used at any desired instant to administer an 
injection into his own body. For that purpose the safety member 28 is 
first removed by exerting a rearward directed force on the cap 44, as a 
result of which the safety pin 45 is pulled away from between the 
resilient prongs 46. By pressing the nose portion 39 of the cartridge 
holder against the body at the area where the injection is to be 
administered, the locking mechanism of the injector is unlocked. The 
rearward movement of the cartridge holder 13 in the outer sleeve 11 causes 
a rearward movement of the inner pistol sleeve in the outer pistol sleeve, 
as a result of which the discharge mechanism is unlocked, exactly as 
described in the British Patent Specification No. 1,449,986 mentioned 
hereinbefore. When the injector has been actuated, the barrel with 
contents and the needle holder with needle move forward, needle holder 
collar 18 and clamping sleeve 23 slidably moving forward in the cartridge 
holder. Upon passing the needle holder shaft, the cartridge holder wall is 
bent slightly outward at the area of the projections 50 so as to allow 
passage of the needle holder shaft ("overridden"). The needle guard is 
compressed between the front face of the needle holder neck and the rear 
face of the front end of the nose portion 39 of the cartridge holder 13, 
the needle 17 piercing the closed end of the needle guard, emanating 
through the aperture 24 in the nose of the cartridge holder, and 
penetrating into the user's body. When the needle is in its foremost 
position, as illustrated in FIG. 5, in which the needle holder is retained 
by a narrowing in the cartridge holder 13 at the area where the nose 
portion 39 begins, or by the force stored in the compressed needle guard, 
the forward movement of the piston begins under the influence of the same 
spring. First, injection liquid from compartment 29 is injected. At the 
instant at which the separating stopper 32 has moved forward over such a 
distance in the shaft of the needle holder that the entrance 34 to the 
slots 22 in the shaft of the needle holder is uncovered for the injection 
liquid in compartment 36, said liquid can reach the injection needle via 
the slots 22 and can be injected. During the same time the injection 
liquid in compartment 37 flows through solvent by-pass 47 into 
compartments 33, the passable stopper 31 remaining in its place, until the 
front face of the piston engages the rear face of the passable stopper. 
When all the injection liquid from compartment 36 has been injected, the 
front face of the separating stopper 30 engages the rear face of the 
separating stopper 32. Under the influence of the spring 26, said stoppers 
are collectively moved forward in the shaft of the needle holder. When the 
stopper 30 has moved forward over such a distance that the entrance 34 to 
the slots in the shaft of the needle holder is uncovered for the injection 
liquid in compartment 33, which situation is shown in FIG. 6, said liquid 
can finally also reach the injection needle via the slots 22 and 35 and 
can ultimately be injected. In the final situation, not shown in the 
Figures, the stoppers and the piston engage each other. The stoppers then 
are in their ultimate forward position, in which the front face of 
separating stopper 32 engages the front end wall of the needle holder 
shaft. 
It will be apparent to those skilled in the art that various modifications 
and variations could be made in the automatic injector of the invention 
without departing from the scope or spirit of the invention.