Automatic injector

Details Automatic injector Automatic injector

1998-12-16

2001-04-03

Bockelman, Mark (Department: 3762)

Surgery

Means for introducing or removing material from body for...

Treating material introduced into or removed from body...

C604S201000, C604S197000

Reexamination Certificate

active

06210369

ABSTRACT:

The present invention relates to automatic injectors for delivering medicament to an injection site.
Basically, an automatic injector is a device for enabling an individual to self-administer a dosage of liquid medicament into his or her flesh. The advantage of automatic injectors is that they contain a measured dosage of a liquid medicament in a sealed sterile cartridge and can be utilized for delivering the medicament into the flesh during emergency situations. Another advantage of automatic injectors is that the self-administration of the medicament is accomplished without the user initially seeing the hypodermic needle through which the medicament is delivered and without having the user to manually force the needle into his or her own flesh. Examples of such known injectors are disclosed in U.S. Pat. Nos. 5,085,641, 5,540,664, 5,569,192 and 5,092,843.
One problem with known automatic injectors is that they usually use a flexible rubber sheath to keep the needle sterile. The rubber sheath slides over the forward end of the needle and is sealed to the needle carrier. The needle carrier in turn is sealed to the forward end of the cartridge. Together, the sealing between the cartridge and the needle carrier and the rubber sheath provide sealed chamber which prevents unsterilized air from contaminating the needle. These rubber sheathes are difficult to assemble onto the needles and are susceptible to tearing during manufacturing. Also the cartridge and needle assembly are oftentimes assembled together separately from the housing components. In this situation, the sheath and needle extend forwardly from the cartridge with no structural housing components protecting them. Thus, the needle can pierce sheath if it is dropped or abutted against a solid contact surface. When the sheath is pierced, the needle and interior surfaces of the sheath are no longer sterile and these components must be disposed of.
Thus, there exists a need for an improved way of maintaining the sterility of the needle within the automatic injector so as to prevent unsterilized air from contaminating the needle and the other sterilized surfaces associated therewith. In order to meet this need, the present invention provides an automatic injector comprising a housing having opposed forward and rearward end portions. The forward end portion is engageable with a portion of flesh defining an injection site. A needle assembly comprises a needle carrier with a sterilized interior, a tubular substantially rigid protective needle cover with a sterilized interior, and a sterilized needle mounted within the needle carrier. The needle has a forward tip portion, a rearward tip portion, and a fluid passageway formed therein open to the forward and rearward tip portions. The needle cover has a substantially rigid tubular wall defining a forwardly facing needle passing opening and a rearwardly facing needle carrier receiving opening. The needle carrier and the needle are mounted within the needle carrier receiving opening.
The needle carrier is movable relative to the housing and the protective needle cover between (1) a normal, inoperative position wherein the needle is disposed entirely within the housing and the needle cover and (2) an injecting position wherein the forward tip portion of the needle extends forwardly of the housing through the needle passing opening in the protective needle cover. The needle assembly further comprises a first sealing member substantially sealing the needle passing opening when the needle is in the inoperative position thereof and a second sealing member having an annular shape and being disposed between the needle carrier and the needle cover so as to substantially seal the needle guide receiving opening of the needle cover when the needle is in the inoperative position thereof. A medicament cartridge has a sealed interior containing a supply of fluid medicament.
The needle carrier has a tubular cartridge mounting portion defining a rearwardly facing opening. The cartridge is mounted to the cartridge mounting portion of the needle carrier. The medicament cartridge is normally sealed from the needle. The medicament cartridge and the needle are constructed and arranged to be fluidly communicated during an automatic injecting operation such that the rearward tip portion of the needle pierces the cartridge and extends rearwardly into the cartridge interior so as to fluidly communicate the fluid passageway of the needle with the cartridge interior and allow the fluid medicament contained in the cartridge interior to flow into the fluid passageway.
A third sealing member has an annular shape and is disposed between the tubular cartridge mounting portion of the needle carrier and the cartridge so as to substantially seal the rearwardly facing opening of the cartridge mounting portion when the cartridge is in the inoperative position thereof. The first, second and third sealing members cooperate with the sterilized interior of the needle cover and the sterilized interior of the needle carrier to define a substantially sealed sterilized needle chamber with the needle disposed therein such that unsterilized ambient air is prevented from entering the needle chamber and contaminating either the needle or the chamber.
A manually operable drive assembly has an actuator extending generally rearwardly from the rearward end portion of the housing. The drive assembly is constructed and arranged such that a user can perform the automatic injecting operation by engaging the forward end portion of the housing with the aforesaid injection site and manually operating the actuator such that the drive assembly moves both the needle to the injecting position thereof and causes the cartridge and the needle to be fluidly communicated so that the forward tip portion of the needle pierces the injection site and the rearward tip portion of the needle pierces the cartridge. The drive assembly then subsequently forcing the fluid medicament outwardly from the cartridge interior through the fluid passageway of the needle and into the injection site.
It can thus be appreciated that an automatic injector constructed in accordance with the principles of this aspect of the invention does not require the use of a problematic rubber sheath to keep the needle sterile. Instead, the three sealing members cooperate to maintain the sterility of the needle and the needle chamber. These sealing members are not mounted directly to the needle and thus will not be pierced or unsealed as easily as the sheath. It is to be understood that the needle cover does not have to be of the extendible type which moves forwardly to protect the needle after the injection operation has been performed. Instead, the needle cover could serve to protect the needle only during assembly. However, the extendible needle cover is preferred for safety reasons.
Another aspect of the present invention relates to the provision of a removal resistant cap. In automatic injectors it is desirable to provide a cap which is not easily removable so that the actuator is not accidentally operated. For example, it may desirable to prevent children from accidentally actuating the drive assembly of an injector. Also, it would be undesirable to have the cap unintentionally fall off, thereby exposing the actuator. Current actuator caps or covers are easily removed simply by turning the cap until a set of lugs is aligned with corresponding grooves or openings in the housing rear end. An example of this type of arrangement is disclosed in commonly owned U.S. Pat. No. 5,085,641. The arrangement disclosed in the '641 patent is suitable for applications in which it is desired not to make removal of the cap too difficult. For example, in some applications it is desirable that children and other persons with limited manual dexterity should be able to use the injector in an emergency situation. However, in certain applications it is undesirable that a child should be able to remove the cap and operate the injector. Thus, there exists a need for an automatic injector with an actua

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