US3024750A

US3024750A - Automatic locking stitch control system for sewing and the like machines

Info

Publication number: US3024750A
Application number: US757834A
Authority: US
Inventors: Winz Karl
Original assignee: GM Pfaff AG
Current assignee: GM Pfaff AG
Priority date: 1957-08-31
Filing date: 1958-08-28
Publication date: 1962-03-13
Anticipated expiration: 1979-03-13
Also published as: FR1201766A; GB873852A; DE1093183B

Description

March 13, 1962 w AUTOMATIC LOCKING STITCH CONTROL SYSTEM FOR SEWING AND THE LIKE MACHINES 2 Sheets-Sheet 1 Filed Aug. 28, 1958 INVENTOR.

m\ m wm/z BY WW/h March 13, 1962 K. WINZ 3,024,750

AUTOMATIC LOCKING STITCH CONTROL SYSTEM FOR SEWING AND THE LIKE MACHINES Filed Aug. 28, 1958 2 Sheets-Sheet 2 ATTO R N EY tates Patent Ofiiice 3,024,750 Patented Mar. 13, 1962 3,024,750 AUTOMATIC LOCKING STITCH CONTROL SYS- TEM FOR SEWING AND THE LIKE MACHINES Karl Winz, Kaiserslautern, Pfalz, Germany, assignor to G. M. Pfaff A.G., Kaiserslautern, Pfalz, Germany, a corporation of Germany Filed Aug. 28, 1958, Ser. No. 757,834 Claims priority, application Germany Aug. 31, 1957 Claims. (Cl. 112-203) The present invention relates to an electric control system for sewing and the like machines of the type equipped with an electrically operable stitch control device, to change from forward to reverse stitching, and vice versa. More particularly, the invention is concerned with the production of a pre-determined number of forward and reverse locking or backtacking stitches at a desired position, including the starting and end position, of a seam being sewn by said machine. The backtacker or stitch reversing device being normally urged, by a spring or the like, to a position for forward stitching may be operated in a known manner by a solenoid having a control magnet or an equivalent electrically operable actuating means, to change to reverse stitching during the energization thereof by an electric control current.

In producing locking or backtacking stitches of this type, in accordance with conventional methods and practice, such as to lock a seam at its beginning or starting point, the operator had to slow down the machine, such as by the operation of a knee-lever or equivalent control member, in order to be able first to count a desired number of forward looking stitches, to subsequently count the same number of reverse locking stitches upon operation of the machine from forward to reverse stitching and, finally, to return to forward stitching for the sewing and completion of the seam. The same applies to the pro duction of a group of locking stitches at any other point, such as at the end of the seam being sewn by the machine.

This method as used in the past is both time consuming and dependent to a large extent upon the personal factor, whereby to require skilled labor, aside from other shortcomings and drawbacks as will be obvious.

Accordingly, an important object of the present invention is the provision of an electric control system for sewing machines equipped with electrically operable stitch control means to change from forward to reverse stitching, and vice verse, by which the above and related difficulties are substantially overcome or minimized.

A more specific object of the invention is the provision of a control system of the type mentioned, whereby a predetermined number of forward and reverse locking stitches may be produced positively and securely at a desired point of a seam being sewn by a sewing machine.

Another object of the invention is the provision of a locking stitch control system of this type by means of which a desired number of locking stitches may be produced at normal operating speed of a sewing machine economically and expeditiously, as Well as substantially free from the effects of the personal factor and other defects inherent in the previously known methods.

Yet another object of the invention is the provision of a locking stitch control system of th above type, whereby the number of automatically produced locking stitches may be pre-selected, to suit any existing operating or sewing conditions and requirements.

A further object of the invention is the provision of a locking stitch control system for sewing machines, to automatically eflfect a selectable number of forward and reverse locking stitches at a desired point of a seam being sewn by said machine, said system being in operative condition during the actual lock stitching operation only 2 and being returned to rest or inoperative position upon completion of the locking stitch operation, to be ready for the initiation of a renewed operation in connection with either the same or a different seam being sewn by said machine.

The invention, as to its ancillary objects as well as novel aspects, will be better understood from the following detailed description, taken in reference to the accompanying drawing forming part of this specification and wherein:

FIG. 1 is a perspective view of a sewing machine embodying control means according to the invention;

FIG. 2 is a partial view of the presser foot and work and illustrating the sewing of the locking or backtacking stitches; and

FIG. 3 is a circuit diagram of a complete electric control system for the automatic sewing of backtacking or locking stitches as shown by FIG. 2.

Like reference characters denote like parts in the different views of the drawings.

With the foregoing objects in view, the invention involves generally the provision of an electric control systern or device for sewing machines of the type described and adapted to automatically effect, at normal operating speed of the machine, a predetermined number of forward and reverse locking stitches at a desired point, including the starting and end points, of a seam being sewn by said machine, the number of locking stitches being pre-selectable by the operator, to suit existing sewing conditions and requirements.

With these aims in view, the invention contemplates generally the utilization of a synchronous pulse generator driven from the drive shaft or an equivalent operative organ of a sewing machine, to produce a series of electric counting pulses, each pulse preferably representing a single stitching operation and being applied to a pulse counter, for example a conventional stepping switch or relay. The stepping switch may comprise a movable contact cooperating with a plurality of stationary contacts progressively engaged by said movable contacts in synchronism with the succession of stitch counting pulses. The stationary contacts of the stepping switch are, in turn, connected, preferably through a relay or the like, with the electrical control circuit of the backtacker or stitch reversing device, such as through an electromagnetic solenoid control device, by way of a multiple-element pre-selector switch, in such a manner as to provide a plurality of branch circuits and to energize said stitch reversing device, to change from forward to reverse stitching upon the occurrence of a pre-selected number of counting pulses and completion of a corresponding number of forward locking stitches. Furthermore, said selector switch elements may be mutually interconnected, to cause an equal number of reverse locking stitches superimposed upon said forward locking stitches and to de-energize said stitch reversing device and to return the same to the forward stitiching direction for the normal sewing of a seam by the machine. Additional means may be provided to return the pulse counter or step-ping switch to its zero or starting position upon reaching the final counting pulse or contact of the stepping switch and, furthermore, the pulse counter circuit may be normally interrupted and connected to start counting of the stitches or pulses at the desired instant or position of the seam, where the sewing of locking or tacking stitches is desired. Thus, where the look ing stitches are desired at the start of a scam, the counting circuit may be closed at the time of starting of the stitching opentaion, to initiate the counting of the forward locking stitches. Alternatively, the counting pulses may be started at any other position of the seam, such as by means of a separate stitch counter or synchronous timing device, to initiate the sewing of a pre-determined group of locking stitches at a desired point, including the beginning and end of a seam being sewn by the machine.

Referring more particularly to FIG. 1 of the drawings, the sewing machine shown, being of standard and conventional construction, comprises a stitch direction control or backtacker 11 normally urged to a position for forward stitching by means of a return spring or the like and operable to a reverse stitching position by the electromagnet or solenoid 9 through a chain 9 or the like coupling member. The machine furthermore comprises a stitch counter in the form of a cam 10 mounted upon the arm shaft 12 and controlling a circuit interrupter or make and break device 10, to produce a counting pulse for each operating cycle or stitch being sewn by the machine, in a manner readily understood.

FIG. 2 illustrates the ordinary way of producing the backtacking or locking stitches in a pair of work pieces M and M at the starting point of the seam by first sewing a limited number, say three, forward locking stitches, as indicated by the arrow a in the drawing, placing the stitch control in reverse and sewing the same number of reverse locking stitches, as indicated by the arrow b, and finally returning to forward stitching, to continue the scam s, as indicated by the arrow 0.

Referring to the control circuit, FIG. 3, the reference characters T R S represent a convention three-phase power supply system including a neutral conductor N which serves to supply the three-phase driving motor 2 of the sewing machine, such as a squirrel cage or induction motor, connectable through a main operating switch 1, a pilot lamp 3 being providing to indicate the operative or running condition of the motor. Further connected to the neutral conductor N and one of the phases of the power network is a first bridge rectifier 4, having output terminals 16 and 17 to supply D.C. operating current for the stitch direction control device or solenoid 9, and the primary winding of a step-down transformer 5 energizing a further rectifier 6 having output terminals 7 and 8 to supply D.C. operating current for the stitch control system of the invention. The rectifiers 4 and 6 may be of any suitable type, such as dry or contact rectifiers, PN germanium or silicon junction rectifiers or the like.

The locking stitch control system, shown by way of example, comprises essentially (l) a pulse generator shown in the form of an interrupter switch 10 operated by a cam 10 driven from the drive shaft (see FIG. 1) or an equivalent operative organ of the sewing machine, to produce a series of electric counting current pulses, preferably one for each revolution or stitching operation of the machine, (2) a stopping relay A having a contact 1a, to interrupt the counting pulses upon completion of a locking stitch operation, whereby to normally maintain the control circuit in the non-operative or rest position and to establish its operative condition only just prior to the instant when a locking stitch operation is desired at a pre-determined point of a seam being sewn by the machine, (3) a starting relay B having a contact 2b, to operate the stitch direction control device from forward to reverse stitching upon the occurrence of a pre-selected number of forward locking stitches, (4) a multiple pre-selector switch C for selecting a desired number of locking stitches having switch elements or groups of switch elements or units 10 to 5c, in the example illustrated in the drawing, and (5) a locking stitch counter, for example, in the form of a stepping switch or relay having a control magnet D energized by said counting pulses and having

movable contact arms

3d, 4d and 5d arranged for synchronous operation, as indicated by the dot-dash line 11, and cooperating stationary contacts 3d0-3d10, 4d0-4d10 and 5d0-5d10, respectively. The stepping relay or stitch counter may be constructed in the form of a conventional rotary switch, well known to those skilled in th art, and serves to operate the stitch reversing device through relay B upon the occurrence of a selected number of forward locking stitches, to change from forward to reverse stitching and to return to forward stitching after completion of an equal number of reverse locking stitches, as will become further apparent from the following.

There is further shown in the drawing a monitor or auxiliary switch 12 connected in the pulse counter circuit of the stepping switch magnet D and controlling the operativeness of said counter, a control switch 22 to return the system to inoperative position upon completion of a sewing cycle, further details of the circuit and system being in part described and in part becoming apparent from the following description of the operation of the invention.

When the sewing machine is driven by the motor 2, the interrupter 10 mounted upon the driven shaft of the machine closes once during each revolution or during each stitching operation, the exciting circuit of the magnet coil of the stitch counter D through a circuit being traced as follows:

(1) Terminal 7 of rectifier 6, monitor switch 12, terminal 13, interrupter contact 10, contact In of relay A, terminal 14, step relay coil D, terminal 15 and terminal 8 of rectifier 6.

As a result the

contact arms

3d, 4d and 5d initially engaging the contacts 3d0, 4110 and Sdt) of the respective banks 3d0-3d10, 4d0-4d10 and Sdtl-Sdlt), are advanced from one to the next higher contact by the successive counting pulses controlling the stepping switch.

As an example, let it be assumed at it is desired to produce three locking stitches at the beginning of a seam. For this purpose, the operator closes or presses the contact or group 3c of the pre-selector switch C.

As a consequence, after the pulse generator 10 has closed three times the exciting circuit (I) of the stitch counter or stepping switch magnet D, the

contact arms

3d, 4d and 5d engage the contacts 3d3, 4:13 and 5d3, respectively, whereby a circuit will be closed by way of the contact 3d3 including the starting relay winding B and being traced as follows:

(II) Terminal 7 of rectifier 6, monitor switch 12, terminal 13, winding of the starting relay B, contact 30, contact 3d3, contact arm 3d, terminal 15 and terminal 8 of the rectifier 6.

As a result, the starting relay B closes its contact 2b, whereby to energize the solenoid 9 of the stitch reversing magnet through a circuit traced as follows:

(III) Terminal 16 of rectifier 4, contact 2b, reversing magnet winding 9, and terminal 17 of rectifier 4.

Connected in parallel to the contact 217 of the starting relay is a spark quenching circuit 18 comprising in a known manner an electrical capacitor in series with a high-ohmic resistor. Energization of the reversing magnet 9 in a known manner causes a reversal of the stitching direction or change from forward to reverse stitching, as pointed out hereinahove.

Since the sewing machine continues to operate the circuit (1) will be closed once by each of the next following three counting pulses produced by the interrupter 10, whereby to energize the stitch counting winding D and to advance the contact arms 30?, 4d and 5d to the contacts 3d6, 4d6 and 5:16, respectively. As soon as the contact arm 3d engages the contact 3d6, the exciting circuit (II) for the starting relay B will be interrupted, whereby to open the contact 2b and to interrupt the exciting circuit (HI) of the reversing magnet 9. As a result the feed direction is returned to forward stitching for the normal sewing of a seam by the machine. In this manner, a series of three forward and three backtacking stitches is automatically sewn by the machine, in the manner shown by FIG. 2.

After the machine has sewn, in the cxemplification illustrated, a total of ten stitches, that is after the

contact arms

3d, 4d and 5d have reached the stationary contacts 3d10, 4d10 and 5(110, the exciting circuit for the stopping relay A Will be closed as follows:

(IV) Terminal 7 of rectifier 6, terminal 23, terminal 19, stopping relay winding A, resistor 20, contact 5d10, contact arm 50!, terminal 21, terminal 15, and terminal 8 of rectifier 6.

Excitation of the stopping relay A causes its contact 1a to be opened, whereby to interrupt the circuit (I) of the stitch counter D until the final stoppage of the sewing machine. As soon as the machine has been stopped, an auxiliary switch 22 will be closed, for instance by the lifting of the presser or clamp foot or an equivalent operative organ of the machine, thereby briefly closing a return circuit of the stitch counter being traced as follows:

(V) Terminal 7 of rectifier 6, terminal 23, contact 41110, contact arm 4d, switch 22, terminal 14, magnet coil D, terminal 15 and terminal 8 of rectifier '6.

As a consequence, the

contact arms

3d, 4d and 5d are returned to the starting contacts 4d0, 4d0 and 5d0, while a pilot lamp 24 will be lit by way of the contact 5d0, indicating the readiness of the machine for a renewed locking stitch operation. The circuit for the pilot lamp 24 is traced as follows:

(VI) Terminal 7 of rectifier 6, terminal 23, terminal 19, terminal 25, pilot lamp 24, resistor 26, contact 5:10, contact arm 5d, terminal 21, terminal 15, and terminal 8 of the rectifier 6.

As a result, the exciting circuit (IV) of the stopping relay and the return circuit (V) of the stitch counter D will be interrupted.

If it is desired to produce a different number of locking stitches, for example a maximum of five stitches in the example illustrated, it is necessary to close or depress the contact group So of the selector switch, whereby to effect operation of the starting relay B after five counting pulses or upon engagement by the contact arms 3a, 4a and 5d of contacts '3a'5, M5 and 5d5, respectively, again resulting in the excitation of the reversing magnet 9. The latter becomes de-energized upon the

arms

3d, 4d and 5d leaving the contacts 3d9, M9 and 5119, respectively, that is, after the sewing of five reverse locking stitches and return of the machine in the forward stitching direction, in substantially the same manner as described hereinbefore.

The sewing of the same selected number of forward and reverse locking stitches is enabled by the arithmetically increasing number and interconnection of the switch contact groups 10-50 of the stitch selector switch C, in the manner shown in the drawing and understood from the operation as described hereinbefore.

If it is desired to effect locking of the end of a scam, the monitor switch 12 is maintained in open position until shortly before the completion of the seam and closed by any suitable means, such as by a timing switch or a separate stitch counter of any type designed to close the switch 12 upon completion of a desired number of stitches coinciding with the end position or any intermediate point of a seam where the locking or tacking stitches are desired,

In the foregoing the invention has been described with reference to a specific illustrative device. It will be evident, however, that variations and modifications as well as the substitution of equivalent elements or devices for those shown herein for illustration may be made without departing from the broader scope and spirit of the invention as set forth in the appended claims. The specification and drawing are accordingly to be regarded in an illustrative rather than in a restrictive sense.

I claim:

1. The combination with a sewing machine comprising an electrically actuable stitch control having an exciting circuit, to change from forward to reverse stitching during closing of said circuit; of a control system for automatically producing a selectable number of forward and reverse locking stitches at a predetermined point of a seam being sewn by said machine comprising pulse generating means controlled by said machine, to produce a series of electric pulses starting at the predetermined point of said seam, each pulse representing a stitch being sewn by said machine, stepping switch means controlled by said pulses having movable contact means and a plurality of stationary contacts cooperating therewith, a locking stitch controller comprising a plurality of individual selector switches having progressively increasing numbers of multiple contacts corresponding to varying numbers of locking stitches to be sewn, and multiple circuit connections interconnecting said selector switch contacts with each other, with said stepping switch contacts and said circuit, whereby to close said circuit and to operate said stitch control from forward to reverse stitching upon the sewing of varying numbers of forward locking stitches and to open said circuit and to return said stitch control to forward stitching upon the subsequent sewing of equal numbers of reverse locking stitches by said machine by operation of the respective selector switch of said controller.

2. The combination with a sewing machine comprising an electrically actuatable stitch control having an exciting circuit, to change from forward to reverse stitching during closing of said circuit; of a control system for automatically producing a selectable number of forward and reverse locking stitches at a predetermined point of a seam being sewn by said machine comprising pulse generating means controlled by said machine, to produce a series of electric pulses one for each stitch being sewn by said machine, means to initiate said pulses at the predetermined point of said seam, stepping switch means having a control magnet with means to energize the same by said pulses, a movable contact controlled by said magnet and a plurality of stationary contacts cooperating therewith to progressively advance said movable contact from one to the next stationary contact by said counting pulses, a locking stitch controller comprising a plurality of individual selector switches having progressively increasing numbers of multiple contacts corresponding to varying numbers of locking stitches to be sewn, and multiple circuit connections interconnecting said selector switch contacts with each other, with said stepping switch contacts and with said circuit, whereby to first close said circuit and to operate said stitch control from forward to reverse stitching upon the sewing of varying numbers of forward locking stitches and to open said circuit and to return said stitch control to forward stitching position upon the subsequent sewing of equal numbers of reverse locking stitches by said machine upon operation of the respective selector switch of said controller.

3. In a control system as claimed in claim 2, including means to interrupt said counting pulses upon reaching of the final stationary contact by said movable contact means of said stepping switch.

4. In a control system as claimed in claim 3, including further means to return said moving contact to zero position by said machine upon cessation of the operation thereof.

5. In a control system as claimed in claim 2, wherein said first means is comprised of a cam driven from the drive shaft of said machine, a circuit including a source of current, and an interrupter switch actuated by said cam to produce a current pulse during each revolution of said machine.

6. In a control system as claimed in claim 2, including means to initiate said counting pulses at the instant of starting the stitching of a seam by said machine, to produce a series of forward and reverse locking stitches at the beginning of said seam.

7. In a control system as claimed in claim 2, wherein said first means is comprised of a circuit including a current source and a periodic interrupter controlled by said machine, and a switch in series with said source and interrupter being normally opened and adapted to be closed at a desired instant during a stitching operation, to effect a selected number of locking stitches at a correponding point of a seam being sewn.

8. The combination with a sewing machine comprising a stitch control, an electromagnet having an exciting circuit and an armature connected to said stitch control, to change from forward to reverse stitching during closing of said circuit; of a control system for automatically producing a selectable number of forward and reverse locking stitches at a predetermined point of a seam being sewn by said machine comprising pulse generating means controlled by said machine, to produce a series of electric pulses one for each stitch being sewn, means to initiate said pulses at the predetermined point of said seam, a stepping switch having a control magnet with means to energize the same by said pulses, a movable contact arm controlled by said last-mentioned magnet and a plurality of stationary contacts cooperating therewith, to progressively advance said arm from one to the next stationary contact by said pulses, a locking stitch controller comprising a plurality of selector switches having progressively increasing numbers of multiple contacts corresponding to varying numbers of locking stitches to be sewn, and multiple circuit connections interconnecting said selector switch contacts with each other, with said stepping switch contacts and with said circuit, whereby to first close said circuit and to operate said stitch control from forward to reverse stitching upon the sewing of varying numbers of forward stitches and to open said circuit and to return the stitch control to forward stitching position upon the subsequent sewing of an equal number of reverse locking stitches by said machine by operation of the respective selector switch of said controller.

9. In a sewing machine comprising an electrically actuatable stitch control having an exciting circuit to change from forward to reversed stitching during closing of said circuit; a control system comprising pulse generating means controlled by said machine to produce a series of electric pulses one for each stitch being sewn, means to initiate said pulses at a predetermined point of the seam being sewn, stepping switch means controlled by said pulses, having movable contact means and a plurality of stationary contacts cooperating therewith, to advance said movable contact from one to the next stationary contact by each said current pulses, and multiple circuit connections interconnecting said stationary contacts, said exciting circuit and said movable contact, whereby to first close said circuit and to operate said stitch control from forward to reverse stitching upon the sewing of a predetermined number of forward locking stitches and to subsequently open said circuit and to return said stitch control to forward stitching position upon the sewing of an equal number of reverse locking stitches by said machine.

10. The combination with a sewing machine including electrically actuatable stitch control means having an operating circuit to change from forward to reverse stitching by control of said circuit, of a control system for automatically sewing a selectable number of forward and reverse locking stitches at a predetermined point of a seam being sewn by said machine comprising pulse forming means controlled by said machine to produce a series of electric counting pulses starting at the predetermined point of said seam, each pulse representing a stitch being sewn by said machine, stepping switch means having movable contact means controlled by said pulses and a plurality of cooperating stationary contacts, a locking stitch controller comprising a plurality of multiple-contact selector switches for selecting varying numbers of locking stitches, and circuit means interconnecting said selector switch contacts, said stepping switch contacts and said circuit, whereby to operate said stitch control means from forward to reverse stitching after sewing of a predetermined number of forward locking stitches controlled by the operation of the respective selector switch and to return said stitch control means to its position for forward stitching after sewing of an equal number of reverse locking stitches by said machine.

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