Filter device integrating sampled volume control

1. A drainage device for a filter unit for microbiological testing of liquids, wherein said drainage device comprises:

(a) a mechanical support comprising a reception head for receiving a filter unit including a membrane;

(b) a suction pump connected to said mechanical support to aspirate a liquid substance contained in said filter unit;

(c) a weight sensor on which said mechanical support is mounted and which is adapted to deliver a signal representative of the weight exerted by said mechanical support on said weight sensor;

(d) a user interface for entering data relating to the drainage of said filter unit and/or to said liquid substance; and

(e) a control unit connected to said suction pump, the weight sensor and said user interface, said control unit being adapted to determine, from said data, at least a first weight corresponding to a first representative signal; and in that, when said weight sensor supplies a signal corresponding to said first signal, said control unit starts operation of said suction pump so as to aspirate said liquid substance contained in said filter unit.

2. The drainage device according to claim 1 wherein said reception head comprises a reception surface opposite which said membrane can be disposed and onto which a suction duct discharges, and in that said reception head includes a passage, one end of which discharges externally of said reception surface and the other end of which discharges onto said reception surface, said reception head comprising a selectively operable valve mobile between a first position in which it shuts off said passage and a second position in which it frees said passage.

3. The drainage device according to claim 1 wherein said reception head comprises a selectively operable valve mobile between a first position in which it shuts off said passage and a second position in which it frees said passage, said control unit commands movement of said selectively operable valve into said second position and starts the operation of said suction pump when said weight sensor supplies a stationary signal representative of a constant weight exerted on said weight sensor by said mechanical support after said liquid substance has been aspirated.

4. The drainage device according to claim 1 wherein said reception head comprises a selectively operable valve mobile between a first position in which it shuts off said passage and a second position in which it frees said passage, said control unit commands movement of said selectively operable valve into said second position when said weight sensor supplies signals respectively representative of an upper limit weight when said filter unit, is placed on said reception head and a lower limit weight when said filter unit is removed from said reception head.

5. The drainage device according to claim 1 further comprising a frame, wherein said weight sensor extends substantially horizontally between a first end fastened to said frame and a second end that is free with respect to said frame, and said mechanical support rests on said second end of said weight sensor.

6. The drainage device according to claim 5 further comprising an armature covered with a casing, bearing on a chassis, wherein said frame is suspended from said armature in the space between said chassis and said armature, and an opening in the casing facing said head support is adapted for mounting and demounting a reception head.

7. The drainage device according to claim 1 wherein said mechanical support is connected to said suction pump by a tubular member having at least one flexible portion that extends from said mechanical support substantially perpendicularly to the direction of operation of said weight sensor.

8. The drainage device according to claim 1 further comprising a reception head support entirely fastened to said weight sensor and wherein said reception head is removably fastened to said head support with lockable connecting means.

9. The drainage device according to claim 8 wherein said reception head support has a circular cylindrical projecting vertical portion adapted to cooperate with an opening formed in the portion opposite a reception surface of said reception head and said reception head and said projecting vertical portion are fastened together by keying means to form said lockable connecting means.

10. The drainage device according to claim 8 wherein said reception head has a transverse bore adapted to cooperate with a groove formed around said vertical portion and said transverse bore is adapted to receive removable key means.

11. The drainage device according to claim 8 wherein said head support has an suction branch, one end of which is adapted to be connected to a suction duct of said reception head and the other end of which is adapted to be connected to said suction pump.

12. The drainage device according to claim 8 wherein said head support includes a control device adapted to cooperate with a selectively operable valve to move it into said first position or into said second position.

13. The drainage device according to claim 12 wherein said control device includes a solenoid whose core is adapted to drive said selectively operable valve.