Patent ID: 7237699

Claim:
A filter piston apparatus for dispensing respectively predetermined volumes of pulverulent bulk material, the filter piston having: a hollow-cylindrical piston arranged in a circular-cylindrical bore, a filter which is formed as a plate and is permeable to gas but impermeable to the bulk material, and a metering chamber which accommodates a predetermined volume of bulk material, is present at the end of the circular-cylindrical bore and has a base formed by the filter, the metering chamber being further configured to be attached to a positive-pressure or negative-pressure gas source through the filter, wherein a circumferential wall of the piston has a transverse slot and an inner groove located radially opposite the transverse slot, such that the filter can be pushed at an exterior surface of the circumferential wall of the piston into the slot until the filter is seated in the piston, such that the filter is secured in the slot on both sides of the filter, in the axial direction of the piston, along a peripheral edges of the filter.