Control device for a differential feed of a sewing machine

A control device for a sewing machine with stitch forming means including a needle and differential feed means advancing a workpiece having at least one ply in a sewing direction, comprising:

• first feed means arranged behind said needle with respect to said sewing direction;
• a first feed unit imparting a feed rate to said first feed means;
• first regulating means for altering said feed rate of said first feed means;
• second feed means arranged in front of said needle with respect to said sewing direction;
• a second feed unit imparting a feed rate to said second feed means, and
• second regulating means for altering said feed rate of said second feed means;
• said control device including:
• a control box;
• and
• a control drive controlled by said control box for regulating the relation of said feed rates imparted to said first and second feed means comprising:
• a first pneumatic cylinder operably connected to said first regulating means;
• a second pneumatic cylinder operably connected to said second regulating means and
• a first and a second group of solenoid valves controlled by said control box,
• each of said cylinders including individual cylinders operated by one of said group of solenoid valves.

A control device for a sewing machine having

• a housing including a base plate;
• stitch forming means with a needle and
• differential feed means advancing a single- or multi-ply workpiece in a sewing direction, comprising:
• first feed means arranged behind said needle with respect to said sewing direction;
• a first feed unit installed in said base plate and imparting a feed rate to said first feed means;
• first regulating means for altering said feed rate of said first feed means;
• second feed means arranged in front of said needle with respect to said sewing direction;
• a second feed unit imparting a feed rate to said second feed means;
• and
• second regulating means for altering said feed rate of said second feed means,
• said control device including:
• a control box;
• a control drive controlled by said control box for regulating the relation of said feed rates imparted to said first and second feed means, and comprising:
• a first and a second group of solenoid valves operated by said control box for controlling a compressed air flow;
• a first pneumatic cylinder arranged in said base plate and having individual cylinders operated by said first group of solenoid valves and operably connected to said first regulating means and
• a second pneumatic cylinder arranged in said base plate and having individual cylinders operated by said second group of solenoid valves and operably connected to said second regulating means,
• said first and said second cylinder being composed of equal elements including serially arranged individual cylinders received in a carrier tube and having different strokes forming a proportion of 1:2:4:8.