Pfaff Industriemaschinen Gmbh

G.m. Pfaff Aktiengesellschaft

G.m. Aktiengesellschaft

Karl-Heinz Walther

Albert Dusch

Kurt Arnold

Bernhard Mertel

Horst Zinssmeister

Wolfgang Hauck

Reiner Klein

Walter Hager

Fritz Jehle

Kurt Vollmar

Edgar Butzen

Gunther Denuell

Shortening of needle thread end at the beginning and end of sewing in

A process and device for monitoring the bobbin thread on stitch-forming machines, on the bobbin of which a residual amount of thread is wound in a winding direction opposite the direction of winding of the principal amount of thread, is to ensure that a first control function will be generated at the beginning of consumption of the residual amount of thread, and a second control function is generated nearly without delay in the case of thread end or thread break. To achieve this, two signal patterns are received with a phase shift from a bobbin acting as a signal generator, and the first signal function is generated in the case of a deviation of the actual phase shift from the desired phase shift. If only one signal pattern is received, this first control function is also generated if its signal sequence deviates from a reference signal sequence. The second control function is generated if a stoppage of the bobbin lasts longer than a predeterminable number of stitches. Devices for carrying out this process, as well as a device for winding thread on the bobbin in different directions of rotation for the principal amount of thread and the residual amount of thread are provided.

Process and device for monitoring the bobbin thread on stitch-forming

Lower feed dog lifting, lowering, and horizontal coupling

A device for driving a sewing machine which includes a main shaft driven by a positioning motor that can be stopped in at least one predetermined position and then returned back to a second predetermined position, comprises a coupling disc which can be moved into engagement with a drive disc associated with the motor and a main shaft to drive the main shaft in a direction opposite to its normal direction of operation as determined by the positioning motor. The coupling disc is provided with cam surfaces with a cam engaging surface provided on a supporting member which is biased toward the disc by a predetermined tension. An actuator is connected to the support for rotating the actuator. The initial rotation moves the coupling disc into engagement with the driver disc which is connected to the main shaft, and the further rotation of the support rotates both the coupling and main shaft by a predetermined amount. A predetermined positioning of the actuator determines the amount of rotation of the coupling disc and therefore the main shaft.

Device for driving 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-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

Growing community of inventors

Weilerbach, Germany

Karl-Heinz Walther