Patent ID: 8402903

Claim:
A feed dog device for a sewing machine which includes a table fitted with a needle plate defining a plurality of slots elongated in a longitudinal direction and spaced apart from each other in a transverse direction, said feed dog device comprising: a platform adapted to be mounted under the table of the sewing machine and spaced apart from the needle plate in the transverse direction; a drive member disposed under said platform and having an output shaft which extends upwardly of said platform and which is rotatable about an upright axis; a rotary cam member mounted on and swingable with said output shaft, and defining a cam path which extends angularly about the upright axis and which terminates at forward and backward limits; a cam follower guided by said cam path and disposed such that, when said forward and backward limits are brought to respectively engage said cam follower by virtue of swinging movement of said rotary cam member about the upright axis, said cam follower is displaced radially between proximate and distal positions relative to the upright axis; a lever disposed on said platform to pivot about a fulcrum axis oriented parallel to the upright axis, and having weight and power ends which are configured such that, when said power end is actuated by a torque generated by displacement of said cam follower, said weight end is moved relative to the fulcrum axis by an increased torque between rightward and leftward positions in the transverse direction; a feed dog mount adapted to be mounted under the needle plate and having a feed dog mounted thereon to permit said feed dog to extend through the slots; and a force transmitting unit disposed to couple the increased torque of said weight end to said feed dog mount so as to reciprocatingly move said feed dog in the transverse direction when said weight end is displaced between the rightward and leftward positions, wherein said cam follower is in the form of a follower pin which extends from said power end of said lever in a direction parallel to the fulcrum axis.