Sewing machine for making welted pockets

Claim 1

Sewing machine for making welted pockets comprising an arm carrying a driving shaft, a lock mechanism, a work plate slidable along the longitudinal axis of the machine beneath said arm, a work clamp movable with the work plate to secure thereon a piece of fabric to be sewn, a pair of lateral pressers movable with the work plate and a center blade, said pressers being provided for positioning a patch of fabric over said fabric and thereafter making a suitable folding of said patch, a pair of needles operatively connected to said driving shaft to form two parallel longitudinal stitchings on the fabrics after said folding, the fabrics moving together with the work plate, a cutter movable together with the needles to make a slit on the fabric parallel to the stitchings, vertically movable patch turners and tab slit cutters positioned below the work plate at the end of the displacement of said work plate and pneumatic means to control and actuate the operation of the machine lock mechanism, the movement of the work plate supporting the fabric, the oscillation of the patch turners and the tab slit cutters, the lateral movement of the presser members and the work clamp, pre-set control members being provided in the circuit of said driving means to determine the succession of their operation during the automatic cycle, wherein the means provided for work plate feeding are formed by a pneumatic driving cylinder and a hydraulic fluid control cylinder, the rods of both cylinders being connected to said work plate, the fluid line of said control cylinder having two parallel branches, a pilot valve on one branch and a reducing check valve on the second branch, a rotary valve for causing jogging of said work plate, and an additional reducing check valve, said pilot valve and said reducing check valve being in series with said rotary valve and with said additional reducing check valve.