Pfaff Industriemaschinen Gmbh

G.m. Pfaff Aktiengesellschaft

Reinhold Dobner

Walter Hager

Erich Willenbacher

Bernhard Mertel

Oskar Braun

Ludwig Pietzsch

Knud Overlach

Process and apparatus for preparing a seam

Sewing machine with a thread monitor for the thread of the bobbin

A lighting device for a sewing machine which has a housing with a base and an upright portion mounted on the base and an arm carried by the upright portion which overlies the base in which there is positioned a movable thread needle which operates below the arm to sew materials and which comprises a light source carried in the housing and a flexible sheath supported in the arm of the housing and extends outwardly of the arm in the vicinity of the needle. The sheath carries at least two light guides which have first ends exposed to the light source mounted on the sewing machine housing and an opposite second ends which extend out of the sheath in the vicinity of the needle. The sheath and the light guides are bendable so as to arrange the second ends of the light guide in a selected manner for illuminating selective areas in the vicinity of the needle.

Apparatus for lighting a sewing area of a sewing machine

A sewing machine having a thread monitor associated with a bobbin mounted for rotation. The bobbin includes first and second reflecting surfaces associated with an inner side of a second bobbin flange, and first and second light outlet openings associated with a second bobbin flange. A light source is provided for directing light toward the reflecting surfaces. A light receiver is positioned so as to receive light emerging from the first and second outlet opening. The light receiver produces signals representing the light intensity received by the light receiver. A Schmitt trigger provides a pulse to a microprocessor coinciding with a revolution of the bobbin. For each revolution of the bobbin, an A/D converter converts signals received from the light receiver into digital signals which are compared. The digital signal having the maximum value for the revolution is stored in a memory and then compared with a subsequent maximum value. When the subsequent maximum value differs from the stored maximum value, a warning signal is generated by the microprocessor.

Sewing machine with thread monitor for the bobbin thread

A method of sewing the corners of a double seam, employing a two-needle machine the two needle rods of which each may be mutually independently engaged and disengaged. The method uses control means to arrive at the corner point of the inner seam, disengaging the internal needle rod, furthersewing to the corner point of the outer seam, stopping the sewing machine with the outer needle penetrating the workpiece, then rotating the workpiece, sewing the thus rotated outer seam, and engaging the inner needle rod. The sewing machine comprises at least one adjustable feed dog means, at least one sensor which is disposed ahead of the needles and which triggers the process of positioning the respective needle at the corresponding corner point, said triggering occurring when the edge of the workpiece passes said sensor, a pulse generator coupled to the main shaft of the sewing machine, which pulse generator provides counting pulses for a pulse counter, a microcomputer which controls the operation of the feed dog means in accordance with pulses emitted by the sensor and the pulse generator. To avoid a shortened stitch in the outer seam when forming stitches with the two needles in the region of the corner point of the inner seam, the stitch formation is carried out in two stitch forming cycles, in the first cycle stitch formation by the outer needle rod is prevented, and the advancing is reduced to the stitch length required to reach the corner point of the inner seam, and in the second cycle the inner needle rod is disengaged and the advancing is reduced to the distance comprising the difference between the normal stitch length (as set) and the stitch length executed in the first cycle.

Method of sewing corners of a double seam, with a two-needle sewing

A workpiece prepuncturing device for use with a sewing machine having drive means for reciprocating a needle and means for feeding a workpiece into association with the needle to sew a stitch comprises a perforating tool which is located at a spaced location from the needle which is comparable to a multiple of the stitch length. The perforating tool cooperates with a counter tool which is mounted on the opposite side of the workpiece and is movable toward and away from the workpiece in timed relationship to the speed of the feed and the reciprocation of the perforating tool. The counter tool is supported in a base portion of the sewing machine by an elastic suspension, and it is in drive connection with the main shaft of the machine which operates the needle and the feed for the workpiece.

Sewing machine having workpiece prepuncturing device

A pocket stitch is sewn on cut workpiece parts which are guided into operative association with a reciprocating needle which effects a straight stitch when it is reciprocated and also may be swung from side to side to effect a zig-zag stitching. The workpiece is guided so as to form at least one substantially U-shape straight stitch having spaced apart leg portions and the stitch is secured by guiding the workpiece to effect the formation of a barring stitch at the ends of each leg portion by causing the needle to form a zig-zag stitch at such location. The sewing machine for sewing the pocket cuts includes a needle bar which may be swung during the operation of the drive mechanism or the zig-zag control mechanism may be shifted to effect the formation of a straight stitch. A rotatable cam which is driven by the drive mechanism positions a clamping plate having a substantially U-shape slot which permits reciprocation of the needle through a workpiece carried thereon. The cam includes means for controlling the swinging of the needle to effect the zig-zag stitching and for controlling the straight stitching operation of the needle and it also has means for controlling the shifting of the workpiece to follow the outline. The device can also effect the formation of a double U-shaped stitch in which the U-shape portion is formed by two spaced apart straight stitches and a barring stitch is used at each end of the leg portions which is formed by a zig-zag stitch which is effected transversely to the straight stitches.

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Kaiserslautern, Germany

Reinhold Dobner