An apparatus for accumulating breast milk extracted from a female breast, the apparatus comprising:
- a drain bottle for containing the breast milk,
- a bottle top attachment provided on a bottleneck of the drain bottle,
- a reservoir disposed inside the bottle top attachment, the reservoir having an outlet towards the drain bottle, the reservoir and the drain bottle communicating with each other via a valve provided in the outlet,
- a suction aperture provided in the bottle top attachment and connectable with a suction pump for creating a vacuum in the reservoir,
- an optical sensing device associated with the bottle top attachment and operably coupled to the reservoir and adjusted to measure the volume of the breast milk standing in the reservoir by measuring a liquid level in the reservoir, the optical sensing device comprising a light source and a detector, wherein the light source is configured to emit light towards the reservoir and the detector is configured to detect an intensity of the light emanating from the reservoir, and
- at least one light directing means for directing the light on its path from the light source to the detector,
- a first light guide element of the light directing means is provided between the light source and the reservoir such that light emitted from the light source is redirected by the first light guide element to pass a reservoir wall at a right angle,
- a second light guide element of the light directing means is provided between the reservoir and the detector such that light emanating from the reservoir at a substantially right angle with respect to a reservoir wall is redirected towards the detector, a plurality of light sources are provided in a row transverse to the milk path (P) to face, in a direction essentially parallel to the milk path (P), the first light guide element provided between the light source and the reservoir,
- a plurality of detectors are provided in a row transverse to the milk path (P) to face, in a direction essentially parallel to the milk path (P), the second light guide element provided between the reservoir and the detector,
- the first light guide element provided between the light source and the reservoir comprises a plurality of reflecting surfaces arranged in a first set of stairs at or in the reservoir wall, each reflecting surface being provided at a different height of the reservoir wall and being assigned to one of the light sources,
- the second light guide element provided between the reservoir and the detector comprises a plurality of reflecting surfaces arranged in a second set of stairs at or in the opposite reservoir wall, each reflecting surface being provided at a different height of the opposite reservoir wall and being assigned to one of the detectors, and
- each of the light sources forms a pair with one of the detectors which is provided at the same level in a direction transverse to the milk path (P).