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Blood-taking device
| Details |
Inventors: Hardt, Stefan; Finis, Frank;
Assignee: B. Braun Melsungen AG (Melsungen, DE)
Primary Examiner: Rimell; Sam
Assistant Examiner:
Attorney, Agent or Firm: Loeb & Loeb LLP
A blood-taking device has a comparatively flexible inner tubule and an outer tubule. There is an annular gap between both tubules. The front end of the inner tubule is provided with an end wall pressing against the annular protrusion of an end wall of the outer tubule. In order to fix the inner and outer tubules with respect to each other, the edge of the inner tubule end wall has a locking profile interlocking with a counter profile of the outer tubule. During centrifugation the inwardly directed protrusion sinks into the soft material of the end wall of the inner tubule. Thus, liquid is prevented from entering the annular gap during centrifugation. |
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DETAILED DESCRIPTION In the blood-taking device of the present invention the inner and the outer tubule are engaged by interlocking.
The interlocking engagement is effected at the location at which the inner tubule is strengthened by the end wall and at which it is highly resistant to compression.
The prestressed locking or snap engagement seals the front end of the blood-taking device due to the softness of the material of the inner tubule.
Thus, it is ensured that no air is sucked in through the annular gap when the blood-taking device is filled and that no liquid reaches the annular gap between the outer and the inner tubules after the aspiration process.
Moreover, the locking engagement prevents inadvertent withdrawal of the inner tubule from the outer tubule, e.
g.
when aspirating.
However, the danger of liquid getting into the annular gap not only prevails during the aspiration process when taking blood, i.
e.
while blood flows through the cannula hub of the outer tubule into the inner tubule, but above all when centrifugating.
According to a preferred embodiment of the invention, the centrifugal tightness of the outer tubule is guaranteed by the end wall thereof having at least one annular protrusion surrounding the channel of the cannula hub.
Due to the locking engagement of the inner and the outer tubules, the end wall of the inner tubule rests prestressed on the annular protrusion and is slightly pressed inward.
During centrifugation, this annular protrusion--preferably provided with sharp edges--presses into the bottom of the soft inner tubule, assisted by the pressure exerted by the liquid column in the inner tubule.
It ensures the sealing between the inner and the outer tubules both during aspiration and centrifugation, their prime objective, however, being to provide a seal during centrifugation.
If the cannula hub holds a membrane to be pierced by the cannula, there is a danger during centrifugation that the force exerted by the liquid column contained in the inner tubule will cause liquid to escape along the membrane
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