Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
1999-05-14
2001-07-10
Nguyen, Anh-Tuan T. (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C128SDIG001
Reexamination Certificate
active
06258068
ABSTRACT:
BACKGROUND
The invention relates to devices for administering injectable products, in particular the injection of medically or cosmetically effective products.
Devices which the invention also concerns are known as injection pens. Generally, an injection pen comprises an elongated, hollow cylindrical housing in which a container, having the shape of an ampoule, filled with the product to be administered, is received. An injection needle is attached to the container and when so attached is generally axially aligned with or parallel to the central longitudinal axis of the housing, extending generally from one end of the housing. A drive unit for a piston within the container is also arranged in the housing. The piston is advanced in forward direction within the container under the effect of a driven member of the drive unit, thus causing a predetermined product dose to be dispensed. For advancing the piston, the driven member itself is advanced in the forward direction (i.e., toward the needle) in relation to the housing, either manually or by the drive force of a drive element of the drive unit. In the latter case, energy is stored in the drive unit, which energy is converted into a drive force driving the driven member forward upon the drive unit being actuated.
In the course of advancement of the driven member, the stored energy or at least part of the same is consumed. The drive force exerted by the drive element on the driven member is consequently reduced while the driven member is being advanced. Typically towards the end of the injection or dispensing cycle, the advancing or forward speed of the driven member decreases and, therefore, the dispensing rate will decrease, i.e., dispensing is not uniformly distributed over the total injection or dispensing cycle. Other interferences or counter forces may be caused by irregularities in the internal diameter of the ampoule, resulting in the wall frictional forces affecting the piston, causing non-constant piston movement over the stroke of the piston and making uniform dispensing or injection difficult.
SUMMARY
It is an object of the invention to provide for the uniform dispensing or injecting of an injectable product in devices for administering such products.
In one embodiment, the invention is an injection device comprising a base section and a drive unit including a driven member, a drive element and a damping arrangement. Typically, the base section may accommodate a container from which a product dose is dispensed through a needle by displacement of a piston in the container. The drive unit applies a force to advance the piston in the container to dispense a dose, and the damping arrangement is adapted to generally counteract the drive force and other counter forces produced during use of the device.
In another embodiment according to the invention, a device for administering an injectable product comprises a base section, a container arranged in or on the base section, from which container a product is dispensed through a needle by displacement, in a forward direction, of a piston being arranged in the container, and a drive unit comprising a driven member and a drive element, wherein the drive element exerts a drive force on the driven member upon the drive unit being actuated, thus displacing the driven member in the direction of forward advancement of the piston (toward the needle), thereby advancing the piston within the container. The drive force may be exerted on the driven member by a spring, but also by a pressurized fluid, such as compressed air. For actuation of the drive unit, a blocking means, preventing advancement of the driven member, is released. Preferably, in some embodiments, the drive force is not exerted on the driven member before the release of the blocking means. According to the invention, the device comprises means for generating a controlled damping force, counteracting said drive force in the course of the piston being advanced, in addition to unavoidable counter forces. The unavoidable counter forces essentially are frictional forces acting on the piston when the piston is advanced and any forces generated by the work of displacement the piston performs. Since in addition to these unavoidable counter forces a damping force is generated which counters the drive force, the force difference acting on the driven member and resulting from the drive force, the unavoidable counter forces and the damping force can be controlled much more accurately than is the case in prior art devices.
The damping force is advantageously set to ensure that the product is administered with the most constant dispensing rate possible. In most applications, the dispensing rate is constant upon the piston being advanced at constant speed. Accordingly, the damping force in one embodiment is generated relative to or dependent on the advancing speed of the piston, preferably directly dependent on the advancing speed of the driven member. An acceleration increases the damping force and a deceleration decreases the damping force. If the advancing speed is kept constant, the damping force remains constant. Self-regulation is particularly preferred.
In preferred embodiments, the damping force will be reduced at least once during forward movement. Preferably, the damping force cycle exerted over the advance stroke of the piston is adapted to the cycle of the drive force exerted by the drive element. When the energy of the drive element decreases, the damping force decreases.
In one variation, the damping force is generated by the fact that a volume change work must be performed for the advancement of the piston, due to a chamber increasing or decreasing in volume upon the piston being advanced, with pressure compensation in the chamber only taking place at a delayed rate. This system is self-regulatory since change in speed brings about a corresponding change in the damping force.
In another variation, the damping force itself is a frictional force. Due to the design of the components being in frictional engagement for this purpose, the damping force, in this case caused by friction, is controlled.
The invention is preferably used in injection devices. However, it is not limited to this application. In principle, it may be profitably used in all devices for administering products in which a drive force causes advancement of a driven member, including such devices wherein the drive force directly causes movement of the drive member, and/or in which the advancement of a piston results from the interaction of a drive force with unavoidable counter forces which are predetermined within or result from manufacturing tolerances.
Another object of the invention is to improve removal of a needle safety cap typically applied to the needle in injection devices, in which the needle is surrounded by a needle safety sleeve during transport of the device and only projects over or from a front end of the needle safety sleeve during an injection. In prior art devices of this type, in particular semi-automatic injection devices and fully-automatic injection devices, so-called auto-injectors, the needle safety sleeve is slotted in order to allow the user to remove the needle safety cap by access through the slot. However, this means that the needle is visible in the transport position of the device and, in particular, when inserting the needle, thus possibly producing in the user a psychological barrier against insertion of the needle.
The present invention in large part solves this problem by connecting a stripper to the device in such a way that the stripper is displaceable against the direction of advancement when inserting the needle. Once the stripper has fulfilled its function, i.e. stripped the needle safety cap from the needle, thus allowing simple, complete removal of the cap from the device, the stripper according to the invention does not impede injection, although it is still connected to the device, due to the stripper being either shifted into or over the needle safety sleeve when the needle is being inserted. The needle then also
Heiniger Hanspeter
Hostettler Peter
Jost Stephan
Kirchhofer Fritz
Steck Jürg
Disetronic Licensing AG
Dorsey & Whitney LLP
Nguyen Anh-Tuan T.
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