US Patent 7938073 Air seed meter with debris clearing device

An air seed meter having a rotating disc with seed openings arranged in a circumferential pattern includes a holder adapted to be mounted to the meter housing and carries two balls spring-biased to reciprocate and enter the seed openings as they pass and clear debris from the openings. The balls may also engage dimples on the seed disc located between seed openings or groups of seed openings (in the case of a hill drop planter) in the disc as it rotates to cause vibration in the disc to promote the release of seeds as they exit the vacuum chamber.