Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
2000-08-03
2003-06-10
Scherbel, David A. (Department: 3754)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S110000, C604S194000, C604S195000, C604S208000
Reexamination Certificate
active
06575939
ABSTRACT:
The invention concerns a device for automatically injecting a dose of a medicinal product.
A number of injection devices exist at the present time enabling an inexperienced patient to self-administer a dose of a medicinal product without having to force the needle into himself or herself and actuate the piston of the syringe.
Such injection devices are in particular described in patents EP 516,473, U.S. Pat. No. 3,797,489, U.S. Pat. No. 3,712,301, WO 95/35126, FR 2,654,938, and EP 577 448.
At the present time, for obvious safety reasons, the tendency consists of producing injection devices such as that described in patent EP 516 473, for single use including a propulsion spring designed to inject the medicinal product, and a propulsion spring designed to push the syringe back automatically into the casing after injection. According to this design, the needle of the syringe only projects from the casing during the time of injection and no risk of injury with a soiled needle is therefore to be feared.
Although such injection devices provide an appreciable advantage as regards their safety of use, they however have several disadvantages. In point of fact, in the first place, on account of the manufacturing dimensional tolerances of the syringes, and of the presence of the return propulsion spring, it is virtually impossible to guarantee injection of all the dose enclosed in the said syringes. Now, for certain products such as heparin or specific vaccines, the dose of the product injected must be guaranteed in a very precise manner, a condition which current injection devices cannot systematically fulfill.
Moreover, most of the current injection devices offering this safety of use for the patient prove to have a complexity which leads to a cost price which is hardly compatible with that of a single-use device. Moreover, on account of their design, they generally require the use of specific syringes of which the cost price is out of all proportion with that of conventional syringes used without an automatic injection device.
These last two disadvantages have been overcome by the injection device described in patent application WO 94/21316 which comprises:
a long narrow casing having a front wall pierced by an orifice, and formed of two parts, a front part and a rear part, fitted one into the other and capable of sliding longitudinally in relation to each other over a short traverse so as to be able to undergo a relative movement between two positions: a retracted, so called rest position, of the rear part with respect to the front part obtained naturally in the absence of an external force exerted on the said parts, and a forward, so-called injection position, of the rear part with respect to the front part obtained by means of a longitudinal force exerted on the said rear part,
a syringe disposed in the casing and including a syringe body housing a piston, provided with a finger rest ring and carrying a needle,
a piston rod provided with a collar and extending into the rear extension of the syringe,
means for supporting the collar of the piston rod,
a propulsion spring extending between the means for supporting the collar of the piston rod and the bottom of the rear part of the casing,
means for locking in translation the means for supporting the collar of the piston rod capable of supporting them inside the casing in a position where the propulsion spring is compressed, and where the syringe is entirely housed inside the said casing, and capable of allowing their movement towards a forward position at the end of injection, produced by the propulsion spring, after the parts of the casing are moved from their retracted position to their forward position,
a device for stopping the syringe body in a forward position of the latter where the needle extends at least partially through the orifice of the casing,
means for triggering the means for supporting the collar of the piston rod capable of freeing the said collar, in the forward position of the said supporting means, after the parts of the casing are moved from their forward position to their retracted position,
and a return propulsion spring with a force less than that of the propulsion spring, disposed around the syringe body so as to be compressed by the finger rest ring of the said syringe body when the latter is moved to its forward position.
However, such an injection device does not enable the aforementioned first disadvantage to be overcome, namely to guarantee injection of the entire dose.
The present invention aims to overcome this disadvantage and its object is to provide an automatic injection device designed so as to enable a strictly defined dose of a medicinal product to be injected systematically.
Another object of the invention is to provide an injection device with a simplified design and therefore with a cost price compatible with that of a single-use device.
Another object of the invention is to provide an injection device which can be used with pre-filled syringes of the traditional type.
To this end, the invention concerns a device for automatically injecting a dose of a medicinal product of the type described in patent application WO 94/21316.
According to the invention, this injection device is characterized in that:
it includes means for viewing provided in the wall of the casing so as to enable the means for supporting the collar of the piston rod in their forward position to be seen,
means for supporting the collar of the piston rod comprising:
an inner, so called guide tube, extending into the rear part of the casing so as to delimit a peripheral annular space within the latter adapted so as to house the propulsion spring in the compressed position of the said spring,
a cage with a form adapted so as to slide inside the guide tube, and to house the piston rod and the collar thereof, the said cage including towards one of its ends, the so-called rear end, an internal device for locking the collar of the piston rod capable of deforming radially and, towards its other forward end, a front wall for stopping the propulsion spring and for contacting the means of locking in translation the said supporting means in the retracted position of the latter,
the said guide tube and cage being adapted so that, in the forward position of the supporting means, the device for locking the collar of the piston rod remains imprisoned in the guide tube in the forward relative position of the parts of the casing, and is freed in the retracted relative position of the said parts of the casing.
According to the invention, injection is carried out by applying first of all and in a conventional manner the forward end of the casing against the skin. A pressure exerted on the rear part of the casing then permits the triggering of the propulsion spring and therefore the injection of the product. At the end of this injection, the patient has a visual indication of the end of the traverse which informs him or her that the entire dose has been injected. He or she may then relax the pressure on the rear part of the casing, a relaxation which will enable is this rear part to retract and consequently allow the syringe to return into the casing under the action of the return propulsion spring.
Such an injection device which firstly includes a casing in two parts of which the relative movement enables the tolerances in variations in the lengths of the syringes to be absorbed and enables injection and subsequent return of the syringe inside the casing to be triggered, and secondly includes a visual indication of the end of injection, thus makes it possible to deliver systematically the entire product enclosed in the syringe and moreover constitutes a single-use device eliminating any risk of pricking before and after use.
In addition, absorption of the variation tolerances in the lengths of the syringes is obtained in a very simple manner by providing a sufficient margin concerning the length of the cage remaining imprisoned in the inner tube at the end of injection.
Moreover, the guide tube and the cage preferably have dimensions adapted so
Fristoe John K
Holt William H.
Sanofi-Synthelabo
Scherbel David A.
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