Sewing machine with thread tensioning and take up levers

Sewing machine, comprising at least one needle which moves with alternating motion, taking the upper thread through the piece to be sewn, a shuttle to hook an upper thread to form a loop below the piece to be sewn, a bobbin housing in a bobbin-case located internally in the shuttle, the bobbin containing a lower thread which overlaps the upper thread through the loop, leverage means which act on the upper thread and are mobile with periodic motion between a position where the upper thread is allowed to be fed to the shuttle and a position of complete recovery of the upper thread in which the loop is closed to form a stitch, characterized in that said leverage means comprise at least two mutually independent mobile levers, and that there are provided means of periodically tensioning the upper thread synchronized with movement of said levers, the means of periodically tensioning the upper thread being active in an interval between an instant the first lever completes recovery of the upper thread and an instant the second lever reaches the same position.

Sewing machine, comprising at least one needle which moves with alternating motion, taking the upper thread through the piece to be sewn, a shuttle to hook an upper thread to form a loop below the piece to be sewn, a bobbin housing in a bobbin-case located internally in the shuttle, the bobbin containing a lower thread which overlaps the upper thread through the loop, leverage means which act on the upper thread and are mobile with periodic motion between a position where the upper thread is allowed to be fed to the shuttle and a position of complete recovery of the upper thread in which the loop is closed to form a stitch, characterized in that said leverage means comprise at least two mutually independent mobile levers, and that there are provided means of periodically tensioning the upper thread synchronized with movement of said levers, said shuttle forming a loop whose linear extension is substantially as long as a of length thread drawn out and recovered by said take-up levers.

Sewing machine, comprising at least one needle which moves with alternating motion, taking the upper thread through the piece to be sewn, a shuttle to hook an upper thread to form a loop below the piece to be sewn, a bobbin housing in a bobbin-case located internally in the shuttle, the bobbin containing a lower thread which overlaps the upper thread through the loop, leverage means which act on the upper thread and are mobile with periodic motion between a position where the upper thread is allowed to be fed to the shuttle and a position of complete recovery of the upper thread in which the loop is closed to form a stitch, characterized in that said leverage means comprise at least two mutually independent mobile levers, and that there are provided means of periodically tensioning the upper thread synchronized with movement of said levers, said bobbin-case comprises at least one seat for a location of means for tensioning the lower thread wound on said bobbin.

Sewing machine, comprising at least one needle which moves with alternating motion, taking the tipper thread through the piece to be sewn, a shuttle to hook an upper thread to form a loop below the piece to be sewn, a bobbin housing in a bobbin-case located internally in the shuttle, the bobbin containing a lower thread which overlaps the upper thread through the loop, leverage means which act on the upper thread and are mobile with periodic motion between a position where the upper thread is allowed to be fed to the shuttle and a position of complete recovery of the upper thread in which the loop is closed to form a stitch, characterized in that said leverage means comprise at least two mutually independent mobile levers, and that there are provided means of periodically tensioning the upper thread synchronized with movement of said levers, said bobbin case showing in a position upstream a lower thread passage off the case, when considering the shuttle direction of rotation, a cam shaped circumferential portion axially protruding to shift the upper thread loop from a shuttle path during a last upper thread recovery step.

Method for machine sewing in which a needle carries an upper thread through a piece to be sewn until it is hooked by a shuttle to form a loop around the shuttle below the piece to be sewn, and then is recovered by means of mobile levers moving, together with the needle, characterized by providing the passage of said upper thread through at least two mutually independent mobile levers and by applying a periodic tension to said upper thread synchronized with movement of the levers, the levers moving with periodic motion at the same frequency, a first of said levers being out of phase in advance with respect to a second of said levers.