Abstract: An upper thread carried by a vertically reciprocating needle is drawn from a bobbin through a tensioning device, a supply device and a take-up lever. A predetermined amount of the upper thread is first supplied by actuating the supply device, while applying no tension thereto. An additional amount of the upper thread is then supplied by operation of the take-up lever with a predetermined tension being given thereto. The additional amount is detected by a sensor. The supply device includes a one-way clutch for allowing the upper thread to travel in a predetermined direction which, however, may not be conveyed from the needle side when the supply device is made operative. A CPU controls the amount of thread first supplied by the supply device which will always be smaller than an amount actually required for producing a stitch, resulting in an additional amount to be supplied supplemental in cooperation with the tensioning device.

Abstract: A method of automatically controlling thread tension in a sewing machine according to which a first thread tension device is provided between an upper thread source and a thread take-up lever, and a second thread tension device is provided between the first tension device and the thread take-up lever. The first thread tension device is operated to apply a constant pressure to the upper thread such that the thread take-up lever is able to draw out the upper thread upon moving upward. The second thread tension device is operated to fixedly hold the upper thread until the thread take-up lever moves upward to an upper dead point thereof through a lower dead point thereof, at which the take-up lever moves downward to supply the upper thread to the needle. The second thread tension device is further operated to effect release of the upper thread when the thread take-up lever reaches the upper dead point thereof and until the thread take-up lever moves downward to a thread supply starting position thereof.

Abstract: A sewing machine includes an automatic thread tension adjusting device comprising an upper thread tension member arranged in an a thread running path between an upper thread source and a main thread take-up lever. An auxiliary thread take-up lever is arranged in the upper thread running path between the main thread take-up lever and a needle holding the upper thread. A thread engaging part guides the upper thread. A thread presser is arranged laterally of the upper thread running path between the main and auxiliary thread take-up levers and normally clamps the upper thread. A detector detects a predetermined rotation phase of a drive shaft of the machine and thread elongation, respectively, and generates respective electric signals. A control circuit causes the thread presser to release the upper thread in response to the electric signals generated by the detector.

Abstract: A sewing machine comprises a thread deflecting device arranged between a thread take-up lever and a needle and which in response to a swinging movement of a needle bar effected in response to selection of a zigzag stitch, deflects the upper thread laterally of a fabric feeding direction. A thread blocking device is provided on one side of the thread deflecting device. The sewing machine further comprises an actuator operated in response to actuation of a zigzag stitch pattern selecting key to move the thread blocking device to an operative position thereof. The thread blocking device in the operative position blocks the upper thread as it is deflected in one direction by the thread deflecting device to give a predetermined degree of tension to the upper thread, so that the stitch is tightened on one side of the zigzag stitch in addition to the tightening of the stitch by a thread take-up lever.

Abstract: A main feed bed of a feeding mechanism of a sewing machine of a swinging lever type is provided with a sub-feed bed which is swingable with respect to said main feed bed and is integrally secured with a feed dog. Both feed beds are connected and controlled by respectively independent vertical feed cams, so that a moving locus of the feed dog is made square while keeping the upper surface of the feed dog parallel with the upper surface of a needle plate.

Abstract: A double-function sewing machine, which is provided with a lock stitch forming mechanism and an overlock stitch forming mechanism, has a common driving source and a common flywheel for the two mechanisms. The sewing machine is provided with a switching device which includes a switch key connected to the flywheel of the machine. The switch key is selectively switchable to engage the shaft of the lock stitch-forming mechanism or a drive of the overlock stitch-forming mechanism. The switching device further includes a switching pawl which is engageable with and disengageable from the drive of the overlock stitch forming mechanism to hold the latter when the lock stitch forming mechanism is operated.

Abstract: A thread loop regulating arrangement is provided in a sewing machine having a reciprocated swingable needle carrying an upper thread and a loop taking arrangement including a rotatable loop taker, a bobbin carrier having a predetermined surface to receive thread loops and a bobbin positioned within the bobbin carrier. The thread loop regulating arrangement includes a relatively flat plate placed against the predetermined surface of the bobbin carrier and spaced therefrom and a downwardly extended lip for guiding the thread loop pulled off the bobbin carrier and thereby preventing the formation of undesirable stitches.

Abstract: A lock stitching and overlock stitching machine has a primary driving means, a lock stitching device including a drive shaft, an overlock stitching device including a separate drive shaft and being spaced apart from the lock stitching device, the drive shafts of respective stitching devices being coupled to the primary driving means by a clutch means which is operable to rotate the drive shaft of the lock-stitching device in one direction relative to the user and the drive shaft of the overlock-stitching device in an opposite direction relative to the user.

Abstract: A cycle stitching device for a sewing machine includes a switch automatically operated to deenergize the drive motor of the machine and simultaneously energize a solenoid for activating a stopping device that stops the sewing machine with the needle located at a predetermined position, and pattern cam means stopped at a predetermined position thus permitting the stitching of the subsequent pattern exactly from the initial stitch coordinate.

Abstract: An automatic pattern stitch sewing machine is disclosed in which groups of cams act to engage and disengage cam followers from a plurality of pattern cams and including change-over switches opened and closed in a predetermined sequence when one of the groups of cams reaches a position selecting position.

Abstract: A sewing machine having lock stitching device incorporated in a frame and driven by a primary driving member comprising a detachable overlock stitching device having its own needle bar driving mechanism spaced apart from the stitch forming part of the lock stitching device and driven by the same primary driving means. Preferably, a switching mechanism provides for the actuation of one stitching device while the other is at rest.

Abstract: A sewing machine for making continuous and intermittent stitches has a main shaft which is continuously rotated by a pulley and a clutch mechanism during the making of continuous stitches. The clutch mechanism is repeatedly disengaged by a blocking device when the machine makes intermittent stitches. The blocking device is rotatable, within limits, on the main shaft and can be arrested by a pawl which is mounted on a holder controlled by a stitch selecting cam. The cam can move the pawl nearer to or further away from the blocking device and the pawl has a follower which is located in the path of movement of a second cam, which is integral with the blocking device or rotates with the main shaft, when the stitch selecting cam has moved the pawl nearer to the blocking device whereby the rotating second cam pivots a pallet of the pawl into the path of movement of a shoulder on the blocking device.

Abstract: A zig-zag sewing machine equipped with pattern cams and a pattern cam selection arrangement has a compartment in which various accessories of the sewing machine are accommodated. One lid covers the compartment and another lid overlies the above-mentioned lid, the lids being provided, at their surfaces facing one another, with a table of indicia and with lines connecting the indicia with other indicia provided on a pattern cam selector dial so as to enable the user of the sewing machine to adjust the sewing machine for the particular selected stitch pattern. The lids are mounted for pivoting on a common shaft, and a sliding element is mounted on the shaft for displacement therealong and is visible when the one lid is either open or closed, the position of the slide element being selected in dependence on the selected pattern and also being indicative of the accessory to be used.

Abstract: A sewing machine has a housing and a needle displaceable on the housing between a down position engaging through a workpiece and an up position disengaged therefrom. A drive is connected to a drive wheel rotatable on a drive shaft in the housing that in itself is operatively connected to the needle. A clutch including a clutch member on the shaft between the shaft and the wheel has a control element displaceable between an engaged position for rotationally coupling the wheel and the shaft and a disengaged position for free relative rotation of the wheel and the shaft. Thus in the engaged position of the clutch the drive can vertically reciprocate the needle between its up and down positions. A stopper member having an engaging part is mounted on the shaft and a stopper is mounted on the housing.

Abstract: A sewing machine motor is connected to a drive wheel which can be connected via a clutch to a drive shaft that vertically reciprocates the sewing-machine needle. A cam on the shaft and a stopper on the housing are displaceable between an operative position engageable with each other for stopping rotation of the shaft in a predetermined angular position corresponding to the up position of the needle and an inoperative position unengageable with each other. A cam is provided for displacing the control element of the clutch from an engaged to a disengaged clutch position on engagement of the stopper in its operative position with the cam so that the shaft can be arrested in a predetermined angular position and is substantially simultaneously rotationally uncoupled from the wheel.

Abstract: A sewing machine operated by a foot controller is provided with a mechanism for stopping the main shaft of the sewing machine in a predetermined position of each revolution thereof, thus to intermittently drive the sewing machine to produce intermittent stitches. The mechanism can be made inoperative allowing the main shaft to continuously rotate, thereby to produce the ordinary continuous stitches.