Pfaff Industriemaschinen Gmbh

Kurt Vollmar

Albert Dusch

Karl-Heinz Walther

Karl H Walther

A presser foot device on a sewing machine has a swingingly driven foot which can be shifted by two compressed air cylinders and piston combination and a spring mechanism into an inoperative position and, for adaptation to different work thicknesses, into a plurality of operating ranges, each with a different height position but constant amplitude of oscillation.

Presser foot device on a sewing machine

A sewing machine includes a presser foot which is driven on a main shaft by an eccentric drive which drives through a toggle mechanism to a crank lever driver which effects the raising of the presser foot synchronously with the upward movement of a sewing machine needle so as to release a workpiece for movement relative to the needle. The presser foot is biased downwardly by a spring which may be adjusted as to its tension. During a sewing operation a driver is moved to a position only slightly disengaged from the lifting surface of the presser foot and during periods of engagement of the presser foot with the workpiece the toggle mechanism ensures that the presser foot engages the workpiece gently, irrespective of the adjusted amount of total lift of the presser foot by the drive mechanism.

Presser foot drive linkage in a sewing machine

A setting mechanism for the feed dog of a sewing machine having a setting member secured to a setting shaft for determining the amount and direction of the feed movement for the feed dog, comprises a reversal lever which is pivotable between two end positions and biased into one of the end positions by a return spring. To be able to vary the setting torque by which the return spring opposes the setting motion of the reversal lever, the other end of the return spring is connected to the reversal lever through a linkage. This linkage includes an end member having its pivotal axis coaxial with the setting shaft. The torque of the return spring, which normally increases with the progressing pivoting of the reversal lever may be reduced by a linkage design wherein the torque acting on the reversal lever through this linkage reverses within the actuating range of the lever.

Reversible feed mechanism for sewing machines

An upper cloth feed in a sewing machine comprises a presser foot and an upper cloth feed foot, each connected over a linkage with a feeding and lifting drive. The drive is connected over a connecting member with a substantially vertically moving carrier for the presser foot. A spring acts on the connecting member, and an idle stroke connection is provided inside the lifting drive. For the adjustable distribution of the pressure force on the two sewing feet, the force of the spring acting on the substantially horizontally moving connecting member is variable. In order to obtain a simple constructional design, the spring presses over a pressure rod on a pressure piece mounted for displacement on the connecting member.

Upper cloth feed in a sewing machine

A sewing machine comprises a rotatable main shaft which drives a needle upwardly and downwardly over a sewing station to sew through material which is moved thereover and which includes a trimming knife mounted adjacent the needle for upward and downward movement for selectively and periodically cutting the material. The trimming knife is driven by a linkage mechanism from an eccentric drive and the eccentric drive is detachably connected between the main shaft and the linkage mechanism and permits the knife to be driven with the mainshaft of the sewing machine or by an independent drive through a separate detachable drive mechanism. In one embodiment a positioning motor is connected to the drive through a hand wheel and an engageable and disengageable clutch so that it may drive a linkage mechanism including an eccentric to move the knife upwardly and downwardly for cutting the material being sewn during the operation of the sewing machine or separately when the sewing machine drive is discontinued. The drive is defined from the positioning motor to the hand wheel and through a clutch to the main shaft of the sewing machine which drives an eccentric for operating the linkage mechanism to reciprocate the knife. Another embodiment includes a separate trimming drive including two free wheel clutch arrangements permitting the knife to be driven synchronously with the sewing machine needle drive as well as its separate drive.

Detachable drive for sewing machine trimming knife

A thread cutter for a zig-zag sewing machine which has a needle which swings transversely to the material feed direction to form a zig-zag seam of predetermined width while the needle is reciprocated to pierce material to be sewn in cooperation with a revolving looper as the material being sewn is moved transverse to the swing direction and includes a cutting knife which cooperates with a movable catcher which is moved in time relationship to the rotation of the looper. The catcher is a plate-like member having an end terminating in the tip and a lateral edge on each side of the tip with one lateral edge having a first barb for engaging one leg of the needle thread loop and an opposite lateral edge having a second barb for engaging another leg of the needle thread loop, the one leading directly to the needle. The catcher is movable with the engaged thread portions into association with the knife to sever the threads so as to obtain a free length of thread ends independent of the piercing position of the needle. The second barb is advantageously staggered relative to the first barb by an amount which is less than the maximum width of the zig zag seam. The thread guide surface is provided next to the second barb which extends toward the catcher tip. The thread catcher may also have a third barb on the same side as the second barb which is provided for each half of the overstitch range for the leg of the thread which leads directly to the needle. The spacing between the barbs are equal to the maximum width of the zig-zag seam.

Thread cutter for a zig-zag sewing machine

A sewing machine has a work bearing surface in a substantially horizontal plane and a cutting device for the work including a bottom knife disposed in the horizontal plane of the work bearing surface and a top knife movable in the vertical direction. The cutting device has a toggle lever transmission drive comprising two articulatedly connected connecting rods, the joint of which is connected with a drive element. One of the two connecting rods is connected, at an outer joint thread with the top knife.

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Weilerbach, Germany

Kurt Vollmar