Such multi chamber ampoules are previously used for storing one or more sensitive medical components, which are to be dissolved in a liquid to form an injectable solution. The solution can not be stored for a longer period of time without becoming deteriorated. However, sensitive medical components of this kind can in most cases be stored for longer periods of time, if they are isolated from the solvent or other substance, which adversely would affect the component. Very often those medical components are present in the ampoule in a freeze-dried state and stored therein in a front chamber provided in said ampoule, which chamber has an outlet opening, which usually is sealed by a membrane, or other seal, which could be removed, ruptured or penetrated by a hollow needle, such as a cannula or the like for taking out the solution. The rear of the front chamber is limited by an axially movable partition, sealingly engaging the inner wall of the ampoule and being located to prevent flow between the rear and the front chambers through an interior or exterior by-pass connection provided in the ampoule. Said partition forms the forward end of a rear chamber, in which the solvent to be added to the sensitive medical component in the front chamber is contained.
By forwardly displacing the partition a communication between the front and the rear chambers will be established through said by-pass connection. The rear end of the rear chamber is sealed by movable seal or plunger.
When the liquid in the rear chamber is to be added to the medical component in the front chamber, the rear seal or the plunger is depressed, which via the incompressible liquid, in turn will move the partition in the same direction. As soon as the partition has been moved so long, that a communication has been established between the two chambers through said by-pass connection, liquid will flow from the rear chamber into the front chamber upon further depression of the plunger.
A very well known problem in the art, is that freeze-dried medical components usually are very sensitive to mechanical influences and will deteriorate if the mechanical stresses become too strong. Thus, during the liquid addition step they require a balanced and smooth flow. In order to solve this problem a lot of devices have been proposed for providing a displacing mechanism, by means of which the plunger or the rear seal of the container can be moved in a controlled manner for obtaining the desired flow into the front chamber. In most cases devices of this kind typically comprise a means for receiving and holding an ampoule and a screw actuator, having a male thread, which cooperates with a corresponding female thread relied with the holding means of said ampoule. The pitch of the threads is low, so that each revolution of the screw actuator results in a very limited axial displacement of the actuator. Thus, in this manner, the plunger will have a smooth axial movement. Such devices have a satisfying performance for obtaining a smooth flow of liquid into the front chamber. However, this kind of prior devices presents a disadvantage in that the screw actuator has to be rotated in the backward direction to the same extent as in the forward direction for returning it to its initial position for the reception of a fresh ampoule. This is a time consuming task with no other purpose than to reset the actuator.
Therefore, there has been a need for a device, by means of which the plunger or the rear seal may be displaced in the forward direction in a smooth and uniform manner to provide a smooth flow, but which permits a quick return of the screw actuator to its initial position.
An example of such a device is disclosed in the PCT-application WO 93/14799, which presents a solution to the aforementioned problem. This prior device includes a screw actuator, having a male thread, cooperating with a female thread for the forward movement of the actuator, which for the reset readily can be brought out of its engagement with the female thread and rapidly be reset to its starting position for the reception of a new ampoule.
The prior device comprises a slotted holder, which include a female thread engagable with a screw actuator, when the longitudinal axes of the holder and of the actuator coincide. The actuator may be tilted about an axis perpendicular to its longitudinal axis and be swung out of the slot of the holder. As a result of this tilting movement, the male and female threads loose their mutual engagement, so that the actuator readily and rapidly may be brought back to its starting position, whereupon the device may be reused after the removal of the emptied ampoule.
Even if this device constitutes a progress in relation to prior solutions as regards quickness in the resetting of the device for reuse, it presents a certain number of drawbacks:
it requires a great number of manipulations for the resetting, PA1 it is rather bulky, PA1 it can only be used for one single determined length of ampoule, and PA1 the manufacture thereof is rather complicated and expensive
and great care must be taken when producing some of the constructional features of the instrument, in particular the producing of the female read in relation to the slot, is delicate.