Cylinder-bed type sewing machine

A cylinder-bed type sewing machine comprising:

• a cylinder unit having an outer periphery;
• a throat plate disposed at a position which is on an upper face of said outer periphery of said cylinder unit and confronts a needle, said throat plate having a hole formed therein;
• a feed dog, disposed in the hole formed in said throat plate, for rearward feeding of a sewing product along the outer periphery of said cylinder unit;
• a needle guard reciprocally and lengthwise moved so as to make contact with the needle under a state in which the needle passes through said throat plate;
• an arcuate feeding active portion formed in said feed dog and having a curvature which is the same as that of said cylinder unit;
• a feed base to which said feed dog is fixedly connected, said feed base defining a notched portion;
• a U-like feed base support, rotated about a shaft which is concentric with the center of said cylinder unit, for slidably and respectively holding said feed base support, and for rotating said feed dog about said shaft;
• a crank shaft disposed in said cylinder unit;
• a feed lifting rock shaft which is driven by said crank shaft rotating in one direction;
• a slide block, formed on a front end portion of said feed lifting rock shaft and fitted into said notched portion formed in said feed base, for vertically reciprocating said feed base so that said arcuate feeding active portion is vertically moved between a position where said arcuate feeding active portion of said feed dog projects from said hole of said throat plate toward the outer peripheral portion of said cylinder unit, and another position where said arcuate feeding active portion is retracted from said hole into said cylinder unit;
• a feed lengthwise shaft which is disposed in said cylinder unit, which is moved by said crank shaft, and which is parallel to said feed lifting rock shaft;
• and
• a connecting link, connecting a front end portion of said feed lengthwise shaft with said feed base, for lengthwise reciprocating said feed base so that said arcuate feeding active portion of said feed dog is reciprocally moved while forming a feeding locus in which said arcuate feeding active portion is moved arcuately and rearward, and also a nonfeeding locus in which said arcuate feeding active portion is moved forward.