Seed drilling units

Claim 1

In a towable seed drilling unit of the type comprising: a seed hopper; a seed chamber communicating with said seed hopper and having a floor formed by a portion of the lower run of an endless belt which is perforated by at least one row of holes along its length, each hole in said belt being sized to contain a single seed; a masking plate located below said endless belt and arranged to unmask at least one hole in said endless belt through which a seed may fall; a coulter located beneath said seed chamber for forming a furrow ahead of said unmasked hole; a furrow closing member located behind said seed chamber for closing said furrow formed by said coulter; a ground contacting front wheel located in front of said coulter; a ground contacting rear wheel located behind said furrow closing member; drive means operably associated with said rear wheel and with said belt for driving said lower run of said endless belt in a direction opposite the direction in which said towable seed drilling unit is towed; a first arm adapted to carry said front wheel and being pivotal about a first substantially horizontal axis; a second arm carrying said rear wheel and being pivotal about a second substantially horizontal axis; and means for adjusting the attitude of the first and second arms relative to the remainder of the unit thereby to adjust the penetration depth of the coulter; the improvement wherein said towable seed drilling unit includes a main frame supporting the said front and rear wheels, a four-bar parallel linkage having a front connecting means adapted for connection to a towing vehicle tow bar, a shaft member pivotally connected to said main frame and forming a rear bar of said parallel linkage oriented parallel to said tow bar, and detachable means for locking said member to said main frame to render said parallel linkage static relative to said tow bar whereby the penetration depth of said coulter is determined by said adjusting means, said detachable means being operable selectively to release said member from said main frame and said front wheel being removable from said unit to render said parallel linkage freely pivotable relative to said tow bar whereby the penetration depth of said coulter is determined by the relation of the towing vehicle to said towable seed drilling unit.