Pfaff Industriemaschinen Gmbh

Firma Pfaff Industriemaschinen Gmbh

Walter Hager

Reinhold Dobner

Kurt Arnold

Kurt Bolldorf

Karl-Heinz Walther

Edgar Butzen

Kurt Petry

Richard Muller

Gunther Denuell

Gunter Tolle

Dieter Balzer

Process and apparatus for preparing a seam

Sewing machine with thread monitor

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

An arrangement for monitoring the shuttle thread reserve in a sewing machine with a lockstitch revolving shuttle and with a light-emitting diode, which sends a beam of light through openings in the bobbin housing and in the bobbin to a photodetector which triggers a switching pulse for an actuating device. To obtain maximum utilization of the residual thread, the photodetector is used at the same time as a pulse generator for a counter which controls the actuating device. The counter can be connected to a switch-off device of a drive motor for the sewing machine.

Apparatus for monitoring shuttle thread supply of a sewing machine

At a work clamp for buttonhole sewing machines, comprising a support plate and a clamping frame arranged at a pivotable carrying lever, spaced from the clamping frame, a hold-down device with a clamping plate resiliently pressed against the work is fastened at the carrying lever. The clamping frame, when raised is pressed into a slanting position by a spring. During the descending movement of the clamping frame and hold-down device, the hold-down device precedes the clamping frame and clamps the work to the support plate. As a next step, the edge of the clamping plate of the clamping frame which is spaced from the hold-down device impinges on the work. A clamping surface of the clamping plate forms an acute angle with the support plate. As the descending movement of the clamping plate continues, the clamping frame swings out about its bearing pin on the carrying lever. At this time the edge engaging the work moves away from the hold-down device. The work is therefore pulled smooth and stretched in the buttonhole sewing area before it is clamped by the clamping plate for the following sewing operation. By this measure, rippling of the area of the work surrounding the buttonhole is prevented.

Work clamp for buttonhole sewing machines

An auxiliary needle is supported by a shiftable and rotatable slide rod which extends in a slightly inclined position relative to the vertical and is guided by an extension in a guide slot. The upper portion of the guide slot extends at an angle relative to the slide rod. Therefore, if moved from its rest position downwardly into its working position, the auxiliary needle performs first a combined rotary and translational motion, and then, upon penetrating a workpiece, only a straight longitudinal motion.

Sewing machine having auxiliary work turning needle

A sewing machine with at least one feed means, the feed amount of which is variable by means of a positioning device acting on at least one positioning gearing; with a system for approaching a predeterminable end point of a seam in spaced relation to the edge of a workpiece; with a sensor disposed before the needle which during passage of the edge triggers the process for the positioning of the needle in the end point; with a pulse generator coupled with the main shaft of the sewing machine for the delivery of counting pulses for a pulse counter and a microcomputer which interrupts the action of the feed means as a function of the pulses emanating from the sensor and from the pulse generator in the end point. For the exact control of the insertion of the needle into the predetermined end point, the microcomputer is connected with a displacement system for an abutment for the presettable limitation of the movement deflection of a follow-up element coupled with the positioning gearing and with a servo system moving the latter against the abutment. For feed reversal immediately after execution of the stitch formation in the end position, the follow-up element is coupled with the positioning gearing through a freewheel coupling. To prevent displacement of the abutment by reaction of the forces occurring when the stitch length is shortened, the displacement system is connected with the abutment through a self-locking gearing.

Sewing machine having a system for approaching a predetermined end point

A sewing machine is with a device for producing corner seams comprising a sensor which is located ahead of the needle and which releases the operation of stopping the needle at a predetermined corner point as soon as an edge of the work passes by. To exactly control the sticking in of the needle at a predetermined corner location, a pulse generator for delivering counting pulses and coupled to the main shaft of the sewing machine, is connected through a switching element to a setting counter, and is effective only during the advance phases of the feed dog motion. In addition, the sensor is connected to the switching element to switch it on as soon as the oblique edge of the work passes by, and the setting counter is connected to a device for instantly stopping the advancing effect of the feed dog, and to a device for stopping the sewing machine in the lowermost position of the needle, to release the operation of these devices as soon as a presettable number of pulses is reached. To instantly stop the advancing effect of the feed dog, the feed dog is connected to its lifting drive through a toggle lever which can be swung out by means of an actuating member controlled by the setting counter.

Sewing machine with equipment for producing corner seams

A sewing machine for making edge-parallel shaping seams in multiple layer articles such as shirt collars comprises a reciprocating needle for sewing through the multiple layers of a workpiece such as a collar which has a plurality of edges disposed at angles to each other. The construction includes a guide fence having a guide edge extending alongside the needle. The material is guided against the guide edge. A feeder engages the workpiece from below a presser foot which is biased against the needle in a working position. The presser foot has an upwardly extending infeed end and a holddown member in the form of a strip element. It is adjustably supported above the workpiece and includes a front edge which is engaged downwardly on the workpiece and extends into the infeed end of the presser foot.

Seamed material edge guide for a sewing machine

A thread-cutting device for sewing machines including a housing mounting a reciprocating thread guiding needle which cooperates with a revolving looper comprises a thread catcher adjacent the looper which is movable to engage the thread and to advance the thread past a fixed knife. The catcher is mounted so that it may move relative to the looper and the fixed knife to urge thread held by the catcher into cutting engagement with the knife. Double action fluid pressure operated piston and cylinder is connected to the catcher so as to move it relative to the knife and to the looper. A member is connected to the mechanism between the fluid pressure cylinder operator and the thread catcher and a spring has one end connected to the member and an opposite end mounted on the housing in such a manner that the force of the spring may be adjusted. A fluid pressure operated control has a movable control piston rod which is engageable with the member in an engagement portion thereof such as an opening therethrough. When engaged, it holds the connection between the fluid pressure operated piston rod and the thread catcher against the influence of the spring. When the spring is connected so that it operates through the member moving the catcher, it causes the catcher to be moved during the cutting movement of the thread with some delay so that tearing of the thread is less likely. In a non-operative position, the control member holds the moving mechanism for the thread catcher against the force of the spring.

Thread-cutting device for sewing machines having a revolving looper

The invention relates to a feed drive for work holders of sewing assemblies, by which, during the formation of the initial stitches of a seam taking place at a low speed, the control cam plate moving the work holder is driven at a reduced speed, and, during the formation of the main part of the seam taking place at a high sewing speed, the control cam plate is driven intermittently in a manner such that at every lowermost position of the needle, the work holder is temporarily stopped. The feed drive comprises a planetary gearing having two inputs, of which the first input can receive a constant rotary motion, and the second input can receive, at the start of the seam formation, a continuous rotary motion which is subtractively superimposed upon the rotary motion at the first input, and, during the ordinary sewing operation, an oscillatory motion whose frequency is equal to the frequency of the needle bar motion.

Sewing assembly with a feed drive for a work holder

The sewing machine has a differential work transport, consisting of a lower main feed and lower and upper auxiliary feeds, with the step sizes of the auxiliary feeds being adjustable, from a step size substantially in accordance with the step size of the main feed, against spring bias. The step sizes are adjusted by respective setting devices having associated setting members connected, through a lever drive, to a common actuating device. The lever drive interconnecting the setting members of the setting devices for the lower and upper auxiliary feeds is operable to vary the step sizes of the lower and upper auxiliary feeds so that one of said lower and upper auxiliary feeds increases as the other of said lower and upper auxiliary feeds decreases. The transmission ratio of the lever drive is adjustable, and the lever drive includes a driver connection operative in one direction only.

Sewing machine with differential work transport

A sewing machine for sewing buttonholes in a workpiece comprises a stationary lower part and an arm having one end pivotally mounted on the lower part and having an opposite end which carries a rotary hook which cooperates with a reciprocating needle carried in the lower part. The arm is pivotal relative to the base part to move the arm from a fixable sewing position with said hook spaced by a predetermined distance from the needle at a stitch-forming area to a rest position in which it is spaced away from the stitch-forming area. A thread-monitoring device is located adjacent the needle for monitoring the thread and detecting any breakage thereof. The machine includes a buttonhole cutting mechanism which is connected to the drive means so as to periodically cut the workpiece. A clamp is carried by the upper arm and it has a lower portion which rests on a resilient support which is biased upwardly by a spring. The upper part of the clamp carries a rod which is biased downwardly by a spring having a lower characteristic than the spring biasing the arm upwardly, and it engages over a presser frame to urge the frame into engagement with the workpiece. A locking mechanism is associated with the support upon which the lower clamping part rests, and it is effective to lock the support arm in a selected position whenever it is actuated by the thread monitor.

Buttonhole sewing machine

A sewing device for producing form seams is usable with a sewing machine having a needle which reiprocates in respect to a cooperating rotary hook. The sewing machine also includes a guide mechanism for guiding a workpiece along a path corresponding to the configuration of the form seam in respect to the needle. The device includes a workpiece support member having a stitch hole for the passage of the needle and a force-away surface bounding the stitch hole. The device includes a plate which is mounted so that the force-away surface is disposed between the needle and the rotary hook and it is mounted for vertical movement and horizontal oscillatory movement. The actuating means for the device causes a movement of the force-away surface in timed relationship to the reciprocation of the needle and in accordance with the movement of the workpiece in a direction opposite to the movement of the workpiece with respect to the needle and the rotary hook.

Sewing device for producing form seams

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.

Growing community of inventors

Kaiserslautern, Germany

Walter Hager