Feed dog device of a sewing machine

Abstract

A feed dog device of a sewing machine includes a driving unit, a needle plate unit, a feed dog unit, an up-down transmitting unit, a horizontal transmitting unit and a direction adjusting unit. The direction adjusting unit includes a stepper motor with a variable rotational speed controlled in accordance with a speed of the driving shaft of the driving unit, and a linkage mechanism actuatable by the stepper motor to be moved to different positions so as to interfere with a horizontal reciprocating motion by the horizontal transmitting unit such that the horizontal reciprocating motion cooperates with the up-down reciprocating motion by the up-down transmitting unit to bring the feed dog unit into performing a variable moving course.

What is claimed is: 
     
         1 . A feed dog device of a sewing machine comprising:
 a driving unit including a driving shaft drivable by a driving member to rotate about a first axis in a longitudinal direction;   a needle plate unit including a needle plate, a needle hole formed in said needle plate, and a plurality of slots formed adjacent to said needle hole;   a feed dog unit including a feed dog mount which receives a transmitting drive from said driving shaft to perform a reciprocating motion, and a feed dog which is mounted on said feed dog mount and which has a plurality of teeth aligned with and extending through said slots;   an up-down transmitting unit coupled between said driving shaft and said feed dog mount to produce an up-down transmitting drive by rotation of said driving shaft to make an up-down reciprocating motion of said feed dog mount in an up-down direction;   a horizontal transmitting unit coupled between said driving shaft and said feed dog mount to produce a horizontal transmitting drive by rotation of said driving shaft to make a horizontal reciprocating motion of said feed dog mount in a horizontal direction that is perpendicular to both the up-down direction and the longitudinal direction; and   a direction adjusting unit including a stepper motor with a variable rotational speed controlled in accordance with a speed of said driving shaft, and a linkage mechanism disposed between said stepper motor and said horizontal transmitting unit, said linkage mechanism being actuated by said stepper motor to be moved between a first linking position and a second linking position, and to interfere with the horizontal reciprocating motion by said horizontal transmitting unit such that the horizontal reciprocating motion cooperates with the up-down reciprocating motion by said up-down transmitting unit to bring said feed dog mount into performing a variable moving course.   
     
     
         2 . The feed dog device as claimed in  claim 1 , wherein said driving unit further includes a drive motor which serves as said driving member and which drives said driving shaft and controls the speed of said driving shaft, said direction adjusting unit further including a controller electrically connected with both said drive motor and said stepper motor, said controller generating pulse signals in accordance with the speed of said driving shaft and sending the pulse signals to said stepper motor so as to control rotation of said stepper motor at the rotational speed proportional to the speed of said driving shaft. 
     
     
         3 . The feed dog device as claimed in  claim 2 , wherein said linkage mechanism has a regulating shaft which is indirectly coupled with and actuatable by said stepper motor to be rotated about a regulating axis that is parallel to and offset from the first axis of said driving shaft, and a regulator which is connected and rotated with said regulating shaft, said regulator having a rail portion, said horizontal transmitting unit including a horizontal cam which is disposed on and synchronously rotatable with said driving shaft, a swingable member which is disposed on and swingable with said horizontal cam, a connecting member which is pivotably connected with both said swingable member and said feed dog mount and rotatable about a second axis that is parallel to and offset from the first axis, and a sliding member which is pivotally connected with an end of said swingable member and slidable along said rail portion of said regulator, said regulator being rotatable synchronously with said regulating shaft to be moved between a first regulating position and a second regulating position at a variable speed,
 wherein, when said linkage mechanism is in the first linking position, said regulator is moved to the first regulating position, said horizontal cam is rotated synchronously with said driving shaft to actuate swing of said swingable member so as to bring said sliding member into reciprocate sliding along said rail portion, and to bring said connecting member into reciprocate swing about the second axis such that said feed dog mount is made to be in the horizontal reciprocating motion in the horizontal direction, and the horizontal reciprocating motion cooperates with the up-down reciprocating motion by said up-down transmitting unit which is driven by said driving shaft to bring said feed dog mount into performing a clockwise feeding moving course relative to said needle plate, where said teeth are moved reciprocately and clockwise relative to said slots, and   wherein, when said linkage mechanism is in the second linking position, said regulator is moved to the second regulating position, said horizontal cam is rotated synchronously with said driving shaft to actuate swing of said swingable member so as to bring said sliding member into reciprocate sliding along said rail portion, and to bring said connecting member into reciprocate swing about the second axis such that said feed dog mount is made to be in the horizontal reciprocating motion in the horizontal direction, and the horizontal reciprocating motion cooperates with the up-down reciprocating motion by said up-down transmitting unit to bring said feed dog mount into performing a counterclockwise feeding moving course relative to said needle plate, where said teeth are moved reciprocately and counterclockwise relative to said slots.   
     
     
         4 . The feed dog device as claimed in  claim 3 , wherein said linkage mechanism further has a transmitting member which is connected with and drivable by said stepper motor to be rotated in both clockwise and counterclockwise directions, a rotary member which is rotatable with said transmitting member, a linking bar which is pivotally connected with an end of said rotary member opposite to said transmitting member, and a regulating arm which is pivotally connected with both said linking bar and said regulating shaft to bring said regulating shaft into rotation about the regulating axis, and wherein, when said linkage mechanism is actuated by said stepper motor to be moved between the first linking position and the second linking position, said regulating arm drives synchronous rotation of said regulating shaft and said regulator to be moved between the first regulating position and the second regulating position. 
     
     
         5 . The feed dog device as claimed in  claim 4 , wherein said transmitting member is in form of a pinion, said rotary member having a toothed end portion which meshes with said transmitting member and which has a first toothed section and a second toothed section, said transmitting member and said rotary member being movable forward and backward with a forward and backward reciprocating drive of said stepper motor between a first meshing position and a second meshing position, wherein, when said linkage mechanism is in the first linking position, said transmitting member and said rotary member are in the first meshing position, where said transmitting member meshes with said first toothed section, and said regulator is moved through said linking bar, said regulating arm and said regulating shaft to the first regulating position, and wherein, when said linkage mechanism is in the second linking position, said transmitting member and said rotary member are in the second meshing position, where said transmitting member meshes with said second toothed section, and said regulator is moved through said linking bar, said regulating arm and said regulating shaft to the second regulating position. 
     
     
         6 . The feed dog device as claimed in  claim 5 , wherein said up-down transmitting unit includes an up-down cam which is disposed on and synchronously rotatable with said driving shaft, and a swing arm which is disposed on and swingable with said up-down cam and which is connected with said feed dog mount to make the up-down reciprocating motion of said feed dog mount.