Injection device and method for its operation

Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...

Reexamination Certificate

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Details

C604S197000

Reexamination Certificate

active

06599272

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an injector device for containers having an opening with or for an injection needle, the container optionally being of syringe type with a bagel of axially roughly constant cross-section, the opening for the needle being arranged at the barrel front and at least one movable wall, optionally with a piston rod connected thereto, inserted in the barrel, the injector for the containers comprising a) a housing, b) a seat or carrier, arranged for reception of the needle or container and for allowing movement thereof, in relation to the housing, in the axial direction between a rear, needle-covering, position and a forward, needle-exposing, position, c) a penetration arrangement operable to move the needle from the rear position to the forward position, d) optionally a return arrangement operable at least to move the needle in the rearward direction, e) an injection arrangement operable at least to expel container content through the needle and f) at least one control button arranged on the housing and operable to at least initiate operation of the penetration arrangement and/or the injection arrangement.
BACKGROUND OF THE INVENTION
Although simple in principle injection procedures based on syringe type devices with injection needles require mastering of several discrete steps. Before the mere injection procedure some initiation actions may be required. Filling the syringe with medication withdrawn from a reservoir such as a vial may be needed, taking into account the proper dose to be administered. In order to avoid this step in the actual treatment situation it is common to provide pre-filled syringes, in which case, however, a dose setting or selecting step may be needed. In its first movement the syringe piston may need an extraordinary break-loose force after storage to overcome both internal reshaping resistance and an increased wall friction due to adherence or depletion of lubricant in contact points. For storage and shelf life reasons pre-filled syringes sometimes are delivered in dual or multiple-chamber form, requiring an additional mixing step immediately before treatment. De-aeration and pre-ejection are generally needed to remove gas in the vessel compartment and fill out spaces for example at the front sealing, outlet attachments and the interior of the outlet devices or needles. The injection procedure proper can be said to involve the basic steps of penetrating the skin with the needle, performing the injection of the medical preparation and withdrawal of the needle from the tissue. The target tissue may differ in e.g. subcutaneous, intramuscular, intracavernosal or intravenous injection and require somewhat different injection techniques, including aspiration steps. Typical problems are full needle penetration into the desired target tissue, injection only after proper location of the needle and full injection of the prescribed dose before the needle is retracted. After injection it is nowadays common to shield or destroy at least the needle to avoid infection transmission by inadvertent secondary needle pricks.
These demands can be met also when using the simplest injection devices, such as the common hypodermic syringe, when in the hands of a skilled operator who also may initiate medically relevant corrective measures in case of accidents and malfunction. However, a general treatment trend is to place administration responsibility on the patients themselves, also in the case of child, elderly and disabled persons. In long-term treatment the patient often develop a certain skill but less frequent administration schemes also exist, often including situations of emergency or patient imbalance. Other unique problems in patient selfadministration, as compared to assistant operated administration, is that less suitable and often strained body positions are required and that apprehended or experienced pain or discomfort may interfere with the medically desirable action pattern. In summary, especially the selfadministration requires more sophisticated devices to facilitate the injection procedure and avoid or reduce risks for mistakes. Patients dependent on daily or occasional administrations also have a legitimate need for convenience and devices discrete enough to be brought around in daily life. Yet it is desirable that such sophistication and convenience is kept simple and inexpensive to allow for widespread distribution and inclusion also in disposable devices.
More or less automated devices has since long existed to enable laymen with limited training performing injections with reasonable safety in critical or emergency situations or to provide an option for patients fearing the needle insertion step. Mechanical automation is provided in common autoinjectors. Typically the user is expected to position the device in proper injection orientation against the skin and operate a trigger button. Stored mechanical energy, e.g. in a spring system, may then perform autopenetration into the tissue, autoinjection of the medical and possibly also automatic needle retraction. Simpler systems may not provide autopenetration but assume the user to make the needle insertion. Generally, once triggering has occurred, either intentionally or inadvertently, the operation sequence proceeds irreversibly. Moreover, the dislocation risks are generally high in mechanical devices due to rebound effects and the forced transitions involved, especially as the forces released may have to be dimensioned for the highest foreseeable operation resistance. Besides being expensive and ungainly, these devices rarely give the patient the experience of full control of the injection procedure and the possibility to halt or correct the injection procedure in case of pain or discomfort.
Automated devices based on electronic or electromechanical principles have also been proposed. The known devices may take advantage of automation principles in several respects, such as the precise and reproducible injection possible with electric motors, motor assisted autopenetration and mixing or reconstitution, cartridge identification, sample analysis, injection data collection and manipulation, dose setting, injector orientation relative gravity for proper mixing or de-aeration etc. Certainly this diversity of possibilities make the automated devices in this class useful in many situations, especially for repeated and frequent use, although the devices tend to be too expensive for broad or disposable use. Again, for patients in favor of personal control the automated functions may be adversely experienced.
On the contrary, simpler manual devices may not at all provide the ergonomic, convenience and safety requirements outlined. A syringe type device for example gives no or little assistance in respect of initiating steps, needle penetration or retraction and requires a cumbersome reverse grip for injection on many body sites and offers no safe sequencing of the various steps involved. Numerous so called “injection pens” have been proposed and marketed, mainly for repeated and regular self-administration, e.g. of insulin or growth hormone, in which multi-dose ampoules are inserted and pre-selected doses delivered, typically by manipulation of an end button. These devices are designed for ease of use in everyday life and facilitate repeated dosing bat do not cure the other problems associated with hypodermic syringes. Also known are injection devices with alternative positioning of control buttons for injection For example, the patent specifications U.S. Pat. Nos. 4,444,560, 4,581,022 and 4,820,287 and WO 96/17640 all disclose a lateral lever with a link arrangement to a piston rod, mainly for the purpose of amplifying the expulsion pressure on viscous dental pastes. Pistol type grips with link arrangements for injection are also known, as exemplified by FR 2717697, mainly for ease of gripping instruments for veterinary mass injection. Also known, as exemplified by FR 2586192, are lateral releasable wheels for fine-tuned movements of needle instruments, mainly for labora

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