Syringe head with warranty seal

A hypodermic syringe head with tamper-evident closure for a syringe barrel, having an injection cannula (4) which is mounted in a cannula carrier (5) from which it protrudes on both axial ends and which is disposed in a cannula carrier guide, so as to be movable relative thereto, and a cannula guard cap (1) , which is adjoined via a rated breaking point (2) by an anchoring element (3) that solidly holds the cannula carrier guide and can be affixed to the barrel neck, wherein a sealing disk (7) is received in the anchoring element, and two axially symmetrical guide grooves (15) for a guide peg (16) of the cannula carrier guide are embodied on the circumference of the cannula carrier, the guide grooves extending at a predetermined inclination substantially to form a V and opening into one another on their end toward the sealing disk, and in the unactuated state of the hypodermic syringe head, the guide peg engages the orifice region (15') of the guide grooves that is oriented toward the sealing disk, and upon a rotation of the cannula guard cap (1) in each of the two directions of rotation, the guide peg slides relative to one of the two guide grooves, destroying the rated breaking point.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a hypodermic syringe head with a tamper-evident 
closure for a syringe barrel, which has a barrel neck that is provided 
with an axial fluid outlet conduit and a circumferential bead for 
anchoring the hypodermic syringe head, having an injection cannula, which 
is mounted in a cannula carrier from which it protrudes on both axial ends 
and which is disposed in a cannula carrier guide so as to be movable 
relative thereto, and a cannula guard cap which is adjoined, via a rated 
breaking point, by an anchoring element that solidly holds the cannula 
carrier guide and can be affixed with elastic deformation to the 
circumferential bead of the barrel neck, and the cannula guard cap has 
axially extending ribs on its inside circumference which engage 
corresponding ribs of the cannula carrier for rotationally driving it. 
2. Description of the Prior Art 
One such hypodermic syringe head is intended to close so-called 
ready-to-use syringes, that is, syringes that are filled with a liquid 
medication and packed in sterile form, with an injection cannula, and are 
sold ready for use. It is understood that these ready-to-use syringes are 
provided with a tamper-evident closure, which makes it possible to see 
whether the syringe is still filled with the original contents and is 
still sterile. The hypodermic syringe head is intended to protect the 
cannula adequately so that upon final mounting of the syringe head on the 
syringe barrel, no damage to or contamination of the cannula can occur. 
For the sake of mass production, a simple construction of the hypodermic 
syringe is also necessary. 
In one hypodermic syringe head of the type defined at the outset above, the 
problem also arises that if the guard cap is unintentionally twisted the 
wrong direction relative to the anchoring element, the rated breaking 
point will indeed break but the cannula will now be forced through the 
sealing disk and put into communication with the medication contained in 
the syringe barrel. 
SUMMARY OF THE INVENTION 
The object of the invention is to create a hypodermic syringe head which in 
conjunction with conventional syringe barrels forms a ready-to-use syringe 
that can not only be constructed simply and under sterile conditions and 
provided with a tamper-evident closure, but also in which provisions are 
taken to prevent mistakes in use with the deleterious effects described. 
The subject of the invention is a hypodermic syringe head with a 
tamper-evident closure for a syringe barrel, which has a barrel neck that 
is provided with an axial fluid outlet conduit and a circumferential bead 
for anchoring the hypodermic syringe head, having an injection cannula, 
which is mounted in a cannula carrier from which it protrudes on both 
axial ends and which is disposed in a cannula carrier guide so as to be 
movable relative thereto, and a cannula guard cap which is adjoined, via a 
rated breaking point, by an anchoring element that solidly holds the 
cannula carrier guide and can be affixed with elastic deformation to the 
circumferential bead of the barrel neck, and the cannula guard cap has 
axially extending ribs on its inside circumference which engage 
corresponding ribs of the cannula carrier for rotationally driving it, 
wherein embodied on the circumference of the cannula carrier are two 
axially symmetrical guide grooves for a guide peg, provided in the 
interior of the cannula carrier guide, which extend with a predetermined 
inclination substantially in a V and open into one another on their end 
oriented toward the sealing disk, and the guide peg, in the unactuated 
state of the hypodermic syringe head, engages the orifice region, oriented 
toward the sealing disk, of the guide grooves and upon a rotation of the 
cannula guard cap in each of the two directions of rotation slides 
relative to one of the two guide grooves, destroying the rated breaking 
point, so that the cannula carrier is rotated and moved together with the 
cannula relative to the sealing disk, wherein an axial introduction 
groove, open at the bottom, for the guide peg adjoins the orifice region, 
oriented toward the sealing disk, of the guide grooves and widens in the 
radial direction towards its inlet end, wherein the end of the injection 
cannula oriented toward the sealing disk is closed and is provided with a 
lateral opening, through which the medication can enter the cannula, after 
the syringe head has been activated, and wherein the sealing disk is 
pre-perforated, and in the unactuated state of the hypodermic syringe head 
the injection cannula closes the hole. 
The hypodermic syringe head constructed according to the invention 
comprises only four separate parts, specifically the guard cap with the 
anchoring element, the sealing disk, the cannula carrier guide, and the 
cannula carrier with the cannula (glued together or high-frequency 
welded), and is therefore simple to produce and assemble. The guard cap 
joined to the anchoring element via a rated breaking point assures the 
temper-evident closure function. The cannula is integrated in protected 
fashion in the syringe head, and upon final assembly, the entire syringe 
head with all four separate parts is mounted as a unit on the syringe 
barrel, so that no damage to or contamination of the injection cannula 
whatever can occur. Once the syringe head has been mounted, the syringe 
barrel can be filled and equipped in sealed fashion with a suitable piston 
unit. 
The activation of the injection is accomplished by twisting the guard cap, 
which breaks the rated breaking point and rotates the cannula carrier into 
the cannula carrier guide, specifically in an arbitrary direction of 
rotation. In the process, the cannula moves relative to the sealing disk, 
thus enabling the medication to enter the cannula. The guard cap is then 
twisted off in the axial direction, and the syringe is ready for 
injection. 
The guide grooves according to the invention on the circumference of the 
cannula carrier guide assure that the guard cap, from its unactuated 
position, that is, while the rated breaking point is still intact, can be 
rotated in both rotational directions to actuate the syringe head, thus 
twisting the cannula carrier into the cannula carrier guide. This 
precludes twisting the guard cap by mistake, severing the rated breaking 
point, without putting the injection cannula into its operative position. 
At the same time, assembly is facilitated by the embodiment according to 
the invention of the guide groove. 
It should be noted that from U.S. Pat. No. 5,250,037, a hypodermic syringe 
head is known in which guide grooves, extending substantially in a V on 
the circumference of the barrel neck are embodied for a guide peg provided 
in the interior of the cannula guard cap. The effect attained by this 
embodiment is that upon actuation of the guard cap in each of the two 
rotational directions, the cannula carrier pierces the sealing disk toward 
the barrel neck. However, the known construction has the disadvantage that 
first, because of how the guard cap is embodied, a germ-free closure is 
not obtained, of the kind achieved in the invention by snapping the guard 
cap onto the circumferential bead of the barrel neck, with elastic 
deformation and the defined rated breaking point. Nor is there any 
non-positive and positive drive of the cannula carrier in the reference, 
of the kind provided in the invention by the mutual rib engagement between 
the guard cap and the cannula carrier. In the construction of the 
invention, assembly is also made easier by the axial introduction groove 
for the guide peg, and moreover, because of the pre-perforated sealing 
disk that in the unactuated state is closed by the cannula, actuation is 
made easier, and the risk that sealing disk material will penetrate the 
cannula is also averted. 
The embodiment according to the invention thus offers optimal freedom from 
germs, with reliable actuation in both rotational directions. 
In a further characteristic of the invention, the inclination of the guide 
grooves is selected such that an approximately one-quarter rotation of the 
cannula carrier causes a travel of approximately 3 mm on the part of the 
cannula relative to the sealing disk. This travel distance assures that 
after an approximately one-quarter rotation, with simultaneous destruction 
of the tamper-evident closure of the cannula guard cap, the cannula will 
have passed so far through the sealing disk that the lateral inlet opening 
of the cannula is opened and the medication can be injected unhindered, 
once the already twisted-off cap has been removed. 
Anchoring the hypodermic syringe head to the syringe barrel can be done by 
press-fitting or by a detent connection. The latter option is preferably 
employed, in which case the anchoring element is made of elastic material 
and is snapped onto the circumferential lead of the neck of the syringe 
barrel. 
A further preferred characteristic of the invention is that the anchoring 
element is embodied conically on the inside, and the cannula carrier guide 
can be press-fitted into the anchoring part from the open end thereof. The 
press fit makes it easier and faster to assemble the ready-to-use syringe. 
The assembly of the ready-to-use syringe can be further simplified if in 
accordance with a preferred characteristic of the invention, an annular 
groove for receiving the sealing disk during assembly is provided on the 
inside of the anchoring element. As a result, the hypodermic syringe head 
can be transported, sterilized, and stored in the fully assembled state 
before being mounted on prepared syringe barrel and piston units. 
One essential advantage of the invention is that the medication does not 
come into contact with the interior of the cannula until the moment the 
ready-to-use syringe is activated, the temper-evident closure is twisted 
off, and the cannula guard cap is removed. This prevents the medication in 
the cannula, during the often very long-term storage of the syringes, from 
crystallizing out and thus also prevents the attendant stopping up of the 
cannula. Because of the described separation between the medication and 
the ready-to-use syringe closure system, sterility is also assured over a 
long period of time. The ready-to-use syringe therefore need not 
additionally be packed in sterile form after production but instead can be 
packed away in boxes without any additional wrapping over it.

DETAILED DESCRIPTION OF THE INVENTION 
The hypodermic syringe head of FIGS. 1 and 2 is composed essentially of 
four separate parts, specifically a guard cap 1, which is integrally 
joined via a rated breaking point 2 to an anchoring element 3; an 
injection cannula 4, which is solidly anchored in a cannula carrier 5, for 
instance by high-frequency welding or adhesive bonding; a cannula carrier 
guide 6; and a sealing disk 7. The cannula carrier 5 is cross-shaped in 
section, as shown in FIG. 3, with four ribs 8 between which radial ribs 1' 
of the cannula guard cap 1 protrude. 
When the hypodermic syringe head is put together, the cannula carrier 5 is 
inserted far enough into the cannula carrier guide 6 that the end 4' of 
the cannula 4 protrudes out of the cannula carrier guide 6 on the side of 
the sealing disk 7. The cannula carrier guide 6 is then introduced into 
the anchoring element 3 and into the guard cap 1, from the free end 
thereof (FIG. 1), and by means of a conical embodiment of the outer 
circumference of the cannula carrier guide 6 and a corresponding conical 
embodiment of the inner wall of the anchoring element 3, an at least 
non-positive press fit is attained. In conclusion, the sealing disk 7 is 
inserted into the anchoring element 3 and snaps into an annular groove 10 
on the inner circumference of the anchoring element 3. The hypodermic 
syringe head thus assembled in final form in this way is shown in FIG. 2 
and can be transported, sterilized and stored without the risk of 
contamination of or damage to the injection cannula 4. 
The sealing disk 7 shown in FIGS. 1 and 2 and 2a forms a diaphragm 7' in 
its central region. 
The end 4' of the injection cannula 4 toward the sealing disk 7 is 
sharpened or, as shown in FIG. 6, closed and provided with a lateral 
opening 11. In the first case, the injection cannula cooperates with a 
sealing disk 7, which in its central region is provided with a diaphragm 
7' that is pierced by the cannula when the syringe is activated. In the 
case of the embodiment of FIG. 6, the sealing disk 7 is pre-perforated, 
and the closed end of the cannula closes the hole 7", which widens 
conically toward the top, before the syringe is activated. The anchoring 
element 3 is made of elastic material and can be snapped, with a 
circumferential groove 12, onto a circumferential lead 13 of the barrel 
neck of the syringe barrel 14. Alternatively, the anchoring element 3 
could be press-fitted onto the barrel neck of the syringe barrel 14 or 
formed onto it by ultrasonic or high- frequency deformation. The syringe 
barrel 14 is filled with a medication and sealed off by the insertion of a 
piston unit K. The hypodermic syringe arrangement thus fully assembled is 
now ready for use. 
To initiate the injection process, the cannula carrier 5 with the injection 
cannula 4 is twisted, by twisting off the guard cap 1, into the cannula 
carrier guide 6 in an arbitrary direction in such a way that in FIGS. 1-5 
the sealing disk 7 is pierced, or in FIG. 6 the opening 11 of the cannula 
4 has passed through the sealing disk 7 sufficiently to reach the region 
of the liquid medication. For the rotational operation of the cannula 
carrier 5 required for this purpose, the guard cap 1 is provided on its 
inner circumference with the four ribs 1', which engage the grooves of the 
cannula carrier or fit between the arms 8 thereof (FIG. 3). By twisting 
the guard cap 1 relative to the anchoring element 3, after the rated 
breaking point 2 has broken, a rotational drive of the cannula carrier 5 
and thus, in FIGS. 1-5, piercing of the sealing disk 7 are brought about. 
The position achieved is shown in FIG. 5. In the embodiment in FIG. 6, the 
end 9 of the cannula, provided with the lateral opening 11, is moved out 
of the position shown in FIG. 6 into the syringe barrel chamber. 
The cannula carrier 5, on its circumference, has two guide grooves 15, 
which extend axially symmetrically with predetermined inclination 
substantially to form a V. The guide grooves 15 open into one another at 
their end toward the sealing disk 7. The orifice region 15' oriented 
toward the sealing disk 7 is engaged by a guide peg 16 of the cannula 
carrier guide 6; when the cannula carrier and cannula carrier guide are 
put together, this guide peg is introduced into the orifice region 15' via 
an introduction groove 17 of the cannula carrier, which groove widens 
radially toward its inlet end. Rotating the guard cap 1 clockwise or 
counterclockwise in this way causes the end 4' of the injection cannula 4 
to pass through the sealing disk 7, or causes the end 9 of the cannula to 
enter the syringe barrel. The inclination of the guide grooves 15 is 
selected such that with a one-quarter rotation of the cannula carrier 5, 
for instance, a travel of the cannula 4 of 3 mm, for example, relative to 
the sealing disk 7 is attained. This distance suffices for the cannula 
guard cap 1 to be twisted off the anchoring element 3 and for the sealing 
disk 7 to have been reliably passed so that the medication can enter the 
void of the cannula through the central opening or the lateral opening 11 
of the cannula 4 and be injected. 
It will be understood that the embodiment shown, with four ribs 1' or arms 
8, is merely an example. Any arbitrary number of ribs, which enable an 
engagement fixed against relative rotation between the guard cap 1 and the 
cannula carrier 5, can be employed. 
The guard cap 1, the anchoring element 3, cannula carrier 5 and cannula 
carrier guide 6 are preferably plastic parts made by injection molding.