Drive and control system in sewing machines producing groups of stitches

Claim 1

In a sewing machine for producing a group of stitches of the time type and having an element to control the beginning and ending of the sewing cycle and cam means to cyclically control the lowering and raising of the work clamp which holds the material to be sewn in a predetermined position during the sewing cycle, a first pneumatic circuit comprising a conduit leading from a source of compressed air to a first piston assembly, a plurality of levers operatively associated with said first piston assembly to selectively engage said sewing cycle control element, a second pneumatic circuit comprising a second piston assembly and three interconnected conduits leading from said source of compressed air to said second piston assembly, means operatively connecting said second piston assembly to said work clamp to move said clamp in response to the direction of flow of air in said second circuit, a control valve in each circuit adjacent said source of compressed air to open and close each circuit to the flow of said air to the respective piston assembly, a common means to selectively operate each of said control valves, a first valve in said second circuit interconnecting the first and second conduits and adapted to be actuated by a said lever to control the flow of air between said first and second conduits and a second valve in said second circuit interconnecting the second and third conduits of said second circuit and leading to said second piston assembly and adapted to be actuated by the cyclic movement of said cam, said second valve comprising means to control the flow of air from said second conduit through said third conduit to said second piston assembly, wherein said first piston assembly is pivotally connected to the end of one arm of a first of said levers which is mounted in a swiveled manner in said sewing machine, the other arm of said first lever being in contact with one arm of a second of said levers pivotally mounted in said machine above said first lever, a second arm of said second lever extends upwardly from said pivotal mounting, means on this last mentioned second arm to lockingly engage said sewing cycle control element, and a third arm of said second lever extends laterally from said first and second arms into operative contact with the first valve of said second pneumatic circuit when the second arm of the second lever lockingly engages said sewing cycle control element.