Upper fabric feed device for sewing machine, utilizing parallel motion mechanism for reciprocating feed foot and presser foot

An upper fabric feed device for a sewing machine, including a frame, a feed foot for feeding a work fabric on a throat plate, a presser foot cooperating with the feed foot to hold the work fabric, and a feet reciprocating mechanism including a drive device, for alternately reciprocating the feed and presser feet to and from lower positions thereof at which said feed and presser feet contact said work fabric on said throat plate, said feet reciprocating mechanism comprising:

• a first swing arm pivotally supported by said frame and pivoted alternately in clockwise and counterclockwise directions by said drive device;
• a parallel motion mechanism including four motion links pivotally connected to each other so as to define a parallelogram having four apexes, said parallel motion mechanism being supported by said frame pivotally about a first one of said four apexes, said four motion links comprising a first pair of adjacent motion links which defines said first apex, and a second pair of adjacent motion links which defines a second one of said four apexes which is opposed to said first apex diagonally of said parallelogram;
• a drive link mechanism including two drive links which pivotally connect said first swing arm to respective two motion links of one of said first and second pairs of adjacent motion links of said parallel motion mechanism;
• a second swing arm pivotally supported by said frame;
• a first connecting link pivotally connected to at least one of said second pair of adjacent motion links of said parallel motion mechanism;
• a triangular lever connected to said first connecting link and said second swing arm;
• a second connecting link and a third connecting link connecting said triangular lever to said feed and presser feet, respectively;
• biasing means for biasing said feed and presser feet toward said throat plate;
• and
• said feet reciprocating mechanism operating such that said feed and presser feet are both placed in said lower positions for contact with said work fabric on said throat plate, when said parallel motion mechanism has a smallest distance between said first and second apexes.