US3780681A

US3780681A - Sewing machine with a needle positioning device

Info

Publication number: US3780681A
Application number: US00212327A
Authority: US
Inventors: T Sasaki
Original assignee: Brother Industries Ltd
Current assignee: Brother Industries Ltd
Priority date: 1970-12-30
Filing date: 1971-12-27
Publication date: 1973-12-25
Anticipated expiration: 1990-12-25
Also published as: GB1360650A; DE2165662C3; DE2165662A1; DE2165662B2; CH536381A; IT942331B

Abstract

A sewing machine so designed as to cause an arm shaft to be subject to different drive controls according to the operating position of a selection knob, though a controller may be continuously depressed in the same manner, wherein, under the first operating position of the knob, the depression of the controller effects continuous normal stitching and the release of the controller brings the arm shaft to rest at a predetermined angular position; under the second operating position of the knob, the depression of the controller causes the arm shaft to make one rotation and be brought to rest at a predetermined angular position regardless of the succession of the depression of the controller; and under the third operating position of the knob, the bobbin winder is actuated with the arm shaft kept inoperative at a predetermined angular position independently of the depression of the controller.

Description

United States Patent [191 Sasaki Dec. 25, 1973 [54] SEWING MACHINE WITH A NEEDLE 2,376,648 5/1945 Anderson 1 12/219 R POSITIONING DEVICE 3,479,976 11/1969 Flach et a1. 1 12/219 R [75] inventor: Toshio Sasaki, lnazawa-chi, Japan [73] Assignee: Brother Kogyo Kabushiki Kaisha,

Mizuho-ku, Nagoya-shi, Japan [22] Filed: Dec. 27, 1971 [21] Appl. No.: 212,327

[30] Foreign Application Priority Data Dec. 30, 1970 Japan 45/125473 Dec. 31, 1970 Japan 45/128236 [52} US. Cl 112/219 A [51 Int. Cl D05b 69/22 [58] Field of Search 112/219 R, 219 A,

[56] References Cited UNITED STATES PATENTS 3,404,767 10/1968 Farnum 112/219 A 3,358,628 12/1967 Kosrow et al.... 112/219 A 2,942,564 6/1960 Larys et a1. 112/219 A 3,388,681 6/1968 Fujita 112/220 3,460,772 8/1969 Bono 112/218 A Primary Examiner-H. Hampton Hunter Att0rney-Robert D. Flynn et a1.

[ 5 7 ABSTRACT A sewing machine so designed as to cause an arm shaft to be subject to different drive controls according to the operating position of a selection knob, though a controller may be continuously depressed in the same manner, wherein, under the first operating position of the knob, the depression of the controller effects continuous normal stitching and the release of the controller brings the'arm shaft to rest at a predetermined angular position; under the second operating position of the knob, the depression of the controller causes the arm shaft to make one rotation and be brought to rest at a predetermined angular position regardless of the succession of the depression of the controller; and under the third operating position of the knob, the bobbin winder is actuated with the arm shaft kept inoperative at a predetermined angular position independently of the depression of the controller.

19 Claims, 23 Drawing Figures PATENTED 3.780.681

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SEWING MACHINE WITH A NEEDLE POSITIONING DEVICE This invention relates to a sewing machine capable of resting the arm shaft at a predetermined angular position thereof and more particularly to a household sewing machine. It is a well-known process to automatically bring, upon completion of sewing, the arm shaft to rest at a predetermined angular position, for example, with the needle positioned above a work fabric. A device for carrying out said process is generally referred to as a needle positioning device.

With a household sewing machine, however, this device has not yet been made commercially available, except for a few cases. This may be due to, among other things, excessive cost, complicated operation and insufficient structural durability. Particularly, the fact that the cost of providing said needle positioning device is too high for the value derived from its use poses the most difficult problem to resolve.

Referring now to a commercially available household sewing machined having the aforementioned process practically adopted, the motor is so designed as to be brought to rest at a point corresponding to the predetermined angular position at which the arm shaft stops. Accordingly, said needle positioning device comprises a first electric circuit for driving the motor at a speed according to the manner in which the controller is depressed; a second electric circuit for operating the motor at a fixed low speed when the controller is released from depression; and switch means for deenergizing the second electric circuit when the arm shaft is brought to rest at a predetermined angular position. From the viewpoint of utility value, however, said needle positioning device is still too expensive to be deemed fully successful in terms of cost.

A mechanism for basting with broad stitch intervals is already disclosed in US. Pat. Nos. 3,433,189, 3,515,082 and 3,598,071. However, there has not yet been proposed a basting mechanism built in the needle positioning device, that is, a type wherein, under normal condition, the arm shaft is continuously driven while the controller is depressed, and brought to rest at a predetermined angular position when the controller is released from depression, but in case of basting, operation of single manual control means causes the arm shaft to make one rotation upon depression of the controller so as to be brought to rest at a predetermined angular position, even though said depression may be continued in the same manner, thereby enabling a single stitch to be formed.

This invention relates to a sewing machine and more particularly to a needle poitioning device for a household sewing machine, said device being so designed as to cause the arm shaft of the machine to be subject to different drive controls according to the operating position of a selection knob, though a controller may be continuously depressed in the same manner.

The sewing machine of this invention has a device for controlling the drive of the arm shaft in many ways, whereby, when the controller is depressed with the selection knob set at the first operating position, the arm shaft of the sewing machine is driven at a speed corresponding to the manner in which the controller is depressed, so as to perform normal stitching; upon release of the controller from depression, the arm shaft makes several rotations at a slow speed to be brought to rest at a predetermined angular position; when the controller is depressed with the selection knob set at the second operating position, the arm shaft makes just one rotation to be brought to rest at a predetermined angu lar position, regardless of the succession of the depression of the controller, so as to form a single stitch, thereby enabling basting to be carried out utilizing said single stitch forming operation; and when the controller is depressed with the selection knob set at the third operating position, the arm shaft is not driven at all, though the controller may be continued to be depressed, but brought to rest at a predetermined angular position, thereby permitting the bobbin winding utilizing the idle rotation around the arm shaft of the drive element connected to the motor.

As mentioned above, this invention provides a household sewing machine whose arm shaft is subject to different drive controls according to the operating position of a selection knob, though a controller may be continuously depressed in the same manner, thus promising application in a wide field and ensuring good utility in terms of cost.

It is accordingly an object of this invention to provide a sewing machine equipped with a novel, improved needle positioning device free from the drawbacks encountered with the prior art type.

Another object of the invention is to provide a sewing machined equipped with a needle positioning device capable of controlling the drive of the arm shaft for normal stitching as well as for basting selectively by single manual control means.

Still another object of the invention is to provide a sewing machine equipped with a needle positioning device capable of controlling the drive of the arm shaft for normal stitching as well as for bobbin winding selectively by a single manual control means.

A further object of the invention is to provide a sewing machined equipped with a needle positioning device capable of controlling the drive of the arm shaft for normal stitching, basting and bobbin winding selectively by a single manual control means.

The present invention can be more fully understood from the following detailed description when taken in conjunction with the appended drawings, in which:

FIG. 1 is a perspective view of a sewing machine according to an embodiment of this invention;

FIG. 2 is a right side view of the sewing machine of FIG. 1, indicating the part arranged according to an embodiment of the invention with the flywheel and cover taken off;

FIG. 3 is a sectional view on line 3-3 of FIG. 2;

FIG. 4 is a side view of FIG. 2 as taken from the right side with a frame taken off;

FIG. 5 is a top view of FIG. 3;

FIG. 6 is a perspective view of the disassembled parts constituting the main section of the sewing machine of 'FIG. 1;

FIG. 7 is a side view, partly in section, of FIG. 5 as taken on line 7-7;

FIG. 8 is a sectional view on line 88 of FIG. 7;

FIG. 9 illustrates an electric circuit used in said sewing machine;

FIG. 10 is a right side view of the sewing machine corresponding to FIG. 2 illustrating the operation of the sewing machined of the invention for normal stitchmg;

FIGS. 1 1 and 12 are right side view of the sewing machine corresponding to FIG. 2 showing the operation of the sewing machine of the invention for basting;

FIG. 13 is a right side view of the sewing machine corresponding to FIG. 2 presenting the operation of the sewing machine of the invention for bobbin winding;

FIGS. 14, and 16 respectively indicate the disassembled parts constituting the selection knob section set for normal stitching, basting and bobbin winding;

FIG. 17 is a sectional view corresponding to FIG. 8 showing a different operating condition therefrom; and

FIGS. 18 to 23 represent another embodiment of the invention: FIG. 18 is a sectional view, partly in section, corresponding to FIG. 3 showing the construction of clutch section and the fitting section of the flywheel; FIG. 19 is a sectional view on line 19-19 of FIG. 18; FIG. is a front view of the flywheel; and FIGS. 21 to 23 are views corresponding to FIGS. 18 to 20 respectively showing changes in the predetermined angular position of the arm shaft.

There will now be described by reference to the appended drawings a sewing machine according to an embodiment of this invention. Referring to FIGS. 1 to 8, the sewing machine of FIG. 1 is a lock stitch type. A machine frame 11 consists of a cylindrical bed 2 disposed on a base 1, a standard 3 erected from the base 1 and a bracket arm 4 supported by the standard 3 so as to overhang above said cylindrical bed 2. An arm shaft 12 of the sewing machine is rotatably mounted on the frame 1 1. This arm shaft 12 controls the operations of all movable parts of the sewing machine including the vertical movement of a needle bar 6 carrying a needle 5 and a thread take-up lever 7. A collar 13 is loosely mounted on the arm shaft 12. A rotary member 14 is secured to one end of the collar 13 through a key 15. Said rotary member 14 rotates by being connected to an electric motor 92 through, for example, a V-belt 16. In that side of the rotary member 14 which possesses a boss section 14a, are formed a spiral groove 14b extending from the base of said boss section 14a and also an annular groove 14c communicated with the terminal portion of the groove 14b and disposed at a lower level than said groove 14b. In this case, the boss section 14a of the rotary member 14 and collor 13 may be integrally formed. A shaftcollar 17 is disposed adjacent to the collar 13 at the end of the arm shaft 12. At that part of the shaft collar 17 which contacts the collar 13 is formed a flange 170. A flywheel 18 is rotatably mounted on the collar shaft 17 and the shifting of the flywheel in the axial direction is restricted by means of a stop ring 18a, and the joint rotation of the arm shaft 12 and the shaft collar 17 is permitted by a connection pin 19. A spriral spring 20 is wound about the cylindrical portion of the collar 13. There is provided a sleeve 21 so as to surround said coil spring 20. One end 20a of the spiral spring 20 is drawn outward through a notch 21a formed in the sleeve 21 to be connected to a pin 22 secured to the flange 17a of the shaft collar 17. The other end of the spiral spring 20 radially extends outward through another notch 21b formed in the sleeve 21 to constitute a projecting end 2012. Thus is constructed in the clutch section of the sewing machine.

An auxiliary frame 23 is secured to the frame 11 by

screws

24, 25 and 26. At the center of the auxiliary frame 23 are erected vertically spaced guide pins 27 and 28 which are fitted into elongate guide holes 29a and 29b perforated in a switch operating lever 29, thereby enabling said lever 29 to be fitted to the auxiliary frame 23 in a vertically movable state. The upper half portion of the switch operating lever 29 is made flat to constitute an engagement portion 29c and the lower portion is bent forward (to the right side of FIG. 3 or to the left side of FIG. 4, as applicable hereinafter) to constitute a shoulder portion 29d, which can be pressed against the actuator 30a of a switch 30, for example, a microswitch fixed to the auxiliary frame 23 so as to be positioned below the switch operating lever 29. While normally left open, said switch 30 is closed when its actuator 30a is depressed by the shoulder portion 29d of said lever 29. Between the shoulder portion 29d of said lever 29 and a spring holding pin 23a erected on the auxiliary frame 23 is stretched an extension spring 31 so as to normally urge said lever 29 to the uppermost position, thereby preventing the shoulder portion 29d of the lever 29 from depressing the actuator 30a of the switch 30. An elongate actuating lever 32 is disposed ahead of said switch operating lever 29 so as to cross it. One end of said actuating lever 32 is pivotally mounted by a pin 35 to the upper part of a supporting lever 34 the lower end of which is pivotably attached to the lower part of the auxiliary frame 23 by a stepped screw 33. At the intermediate part of said actuating lever 32 is formed an upright arm 32a, the end of which is bend rearward (to the left side of FIG. 3 or to the right side of FIG. 4, as applicable hereinafter) substantially at right angles so as to constitute a lug portion 32b. An electromagnetic solenoid 36 is attached by a screw 37 to the fitting portion 23b formed by bending a part of the auxiliary frame 23. To the end of the plunger 36a of said solenoid 36 is connected the other end of the aforesaid actuating lever 32 by a connection pin 38 through an elongate hole 32c perforated in said other end so as to extend lengthwise of said lever 32. Between the connection pin 38 and the spring holding pin 23c erected on the upper part of the auxiliary frame 23 is stretched an extension spring 39 normally to urge the plunger 36a to the uppermost position. When, as later described, there is introduced current through the electromagnetic solenoid 36 to cause the plunger 36a to be pulled downward against the force of the extension spring 39, then the actuating lever 32 rotates about the pin 35 clockwise of FIG. A rockable lever 40 is bent substantially at the center with said bent part pivotally mounted on the auxiliary frame 23 by a screw 41. One end portion of said rockable lever 40 is disposed between the aforesaid switch operating lever 29 and actuating lever 32. At the tip of said one end portion is erected a pin 42 which in turn is fitted into an elongate hole 32d perforated substantially at the center of the actuating lever 32 so as to extend lengthwise thereof. Further substantially at the center of the switch operating lever 29 is bored a vertically elongate hole 29e, into which there is fitted a pin 43 erected substantially at the center of one half arm of the rockable lever 40. The other half arm of the rockable lever 40 is directed downward. At the lower end of said arm is formed an engagement portion 40a so projected as to engage the later described lock cam. An intermediate lever 44 is rotatably fitted by a pin 45 to the supporting portion 23d projectively mounted on the auxiliary frame 23. The lower part of said lever 44 extends below the lug portion 32b of the actuating lever 32. At the end of said lower part is formed a contact portion 44a extending downward slantwise forward (FIGS. 4 and 6). At the top of said intermediate lever is formed a bent portion 44b directed to the boss 14a of the rotary member 14. To said bent portion 44b is rotatably attached by a pin 47 the substantially middle part of a restraining lever 46. At the upper end of the lever 46 is formed an engagement pawl 46a engageable with the spiral groove 14b and annular groove 14c (FIG. 4). At the lower end of said restraining lever 46 is provided on engagement portion 46b bent forward to engage the engagement portion 290 of the switch operating lever 29 from above, thereby maintaining contact between the shoulder portion 29d of the switch operating lever 29 and the actuator 30a of the switch 30. About the collar of the pin 45 is wound a coil spring 48, one end of which engages the fitting portion 23d of the auxiliary frame 23 and the other end of which engages the intermediate lever 44, thereby rendering both intermediate lever 44 and restraining lever 46 pivotally attached thereto rotatable clockwise of FIG. 4. This rotation is restricted according as the engagement pawl 46a of the lever 46 is fitted into the groove 14b or 14c of the rotary member 14. About the collar of the pin 47 is wound a coil spring 49, one end of which engages the intermediate lever 44 and the other end of which engages the restraining lever 46 so as to render said restraining lever 46 rotatable counterclockwise of FIG. 2. This rotation is restricted according as the engagement pawl 46a of the restraining lever 46 is pressed against the inner side walls of the

groove

14b or 140. A stop lever 50 is bent substantially at the middle part with said bent point pivoted to the upper part of the auxiliary frame 23 by a screw 51 and its collar 5 la. One half arm of said stop lever 50 is directed toward the rear side of the upright arm 32a of the actuating lever 32. The upper edge of one end portion of said one half arm acts as a first engagement portion 50a. At the middle point of said edge is projectively provided a second engagement portion 50b engageable with the engagement portion 46b of the restraining lever 46. To the upper end of the upright arm 32a of the actuating lever 32 is pivoted by a pin 53 an engagement member 52. Between one end of said engagement member 52 and the actuating lever 32 is stretched a extension spring 54 normally to render said engagement member 52 rotatable clockwise of FIG. 2, thereby causing the engagement portion 52a of said engagement member 52 formed by bending rearward the tip of its other end portion to engage with the first engagement portion 50a of the stop lever 50. To the end of the other arm of the stop lever 50 is formed a bent engagement strip 50c (FIGS. 3 and 6) directed to the rotating locus of the projecting end 20b of the spiral spring 20. On the lower side wall of said engagement strip 500 is erected a forward extending pin 55, to which there is pivoted an auxiliary engagement strip 56 (FIG. 6). On the lower right side edge of said auxiliary engagement strip 56 (FIGS. 2 and 6) is provided a rearward extending stopper 56a. The upper half of said strip 56 is bent substantially at right angles, with the left side edge of said upper half bent downward to form an engagement portion 56b, and the right side edge thereof bent slantwise downward to constitute an escapement 56c. Between the auxiliary engagement strip 56 and the bent portion of the stop lever 50 is stretched an extension spring 57 normally to render said auxiliary engagement strip 56 rotatable counterclockwise of FIGS. 2 and 6, thereby causing the stopper portion 56a to be pressed against the end of the other arm of the stop lever 50. About the collar 51a is wound a coil spring 58, one end of which engages the auxiliary frame 23 and the other end of which engages the stop lever 50 to render said stop lever 50 rotatable counterclockwise of FIG. 2, thereby causing the engagement portion 56b of the auxiliary engagement strip 56 normally to position on the rotating locus of the projecting end 20b of the spiral spring 20 so as to be engaged with said projecting end b. Accordingly, where the rotary member 14, together with the collar 13, rotates counterclockwise of FIGS. 2 and 6 with the engagement portion 56b of the auxiliary engagement strip 56 kept disengaged from the projecting end 20b of the spiral spring 20, the spiral spring 20 receives by the rotation of the collar 13 a force to cause said spring 20 to be more tightly wound about the collar 13, thereby permitting the joint rotation of the coil spring 20 and collar 13. As the result, the collar 13 and the shaft collar 17 are connected to transmit the rotation of the rotary member 14 to the arm shaft 12. Where, under the aforesaid condition, the engagement portion 56b of the auxiliary engagement strip 56 engages with the projecting end 20b of the spiral spring 20, then said projecting end 20b remains immovable to subject the spiral spring 20 to a force loosening its winding. Accordingly, the spiral spring 20 does not rotate to disconnect the rotary member 14 from the arm shaft 12, resulting in the immediate stoppage of the arm shaft 12. In this case, the aforementioned sleeve 21 presents the excess expansion of the spiral spring 20.

There will now be described the selection knob by reference to FIGS. 2, 3 and 14. In FIG. 3, a selection knob 59 is rotatably mounted on the auxiliary frame 23 by a pin 60.

On the collar of said knob 59 are integrally formed a cam 61 for setting the position of the actuating lever 32, a notch cam 62 and lock cam 63. As shown in FIG. 14, these cams 61 to 63 have a substantially equal maximum radius. The locating cam 61 consists of a first cam plane 61a occupying a relatively small area with a maximum radius, a second cam plane 61b adjacent thereto occupying a relatively small area with a smaller radius than the first cam plane 61a and a third cam plane 61c occupying the remaining area with a still smaller radius. This locating cam 61 is so disposed as to cause the aforesaid cam planes to be pressed against the edge of the supporting lever 34. Between the upper end of the supporting lever 34 and the spring holding pin 23a of the auxiliary frame 23 is stretched an extension spring 64 to render said supporting lever 34 rotatable clockwise of FIGS. 2 and 14, thereby causing the edge of the supporting lever 34 normally to be pressed against the aforesaid cam planes of the locating cam 61. The notch cam 62 comprises a first cam plane 62a occupying an area falling within a range of substantially 200 with a maximum radius, and a second straight cam plane 62b, occupying the remaining area adjacent to said first cam plane 62a said first cam plane 62a having of first to third depressions 62c to 62c formed at a peripheral space of substantially 45. To the underside of the auxiliary frame 23 is fixed a fitting member 65 by screws 66. To said fitting member 65 is attached a notch pin 68 normally caused to deflect upward by a compression spring 67. The engagement portion 68a at the end of the notch pin 68 is engaged with the aforesaid depressions 620 to 62e. The notch cam 62 is so positioned as to have its cam planes pressed against the under edge of the later described actuating lever 70 for bobbin winding, which is pivoted at the intermediate part by a pin 69 to the upper part of the auxiliary frame 23. Between the fitting member 65 and the lower end of the actuating lever 70 is stretched an extension spring 71 to render said lever 70 rotatable counterclockwise of FIGS. 2 and 14, thereby normally pressing the under edge of said actuating lever 70 against the cam planes of the notch cam 62. Thelock cam 63 has first to third depressions 63a to 63c formed at a peripheral space of substantially 45, said depressions 63a to 63e being engageable with the engagement portion 40a of the rockable lever 40.when it rotates clockwise of FIGS. 2 and 14. The relative positions of the cams 61 to 63 are defined as shown in FIGS. 2 and 14, enabling normal stitching, basting and bobbin winding to be selectively carried out by rotation of the selection knob 59.

A support plate 72 (FIGS. 2 and is fixed by screws 73 to the upper part of the frame 11. To said support plate 72 is rotatably fitted by a pin 74 the intermediate part of a rockable lever 75 bent into substantially equal halves. At the end of one arm of said rockable lever 75 is formed a bearing 76, which journaled a rotary spindle 77. To the lower end of said spindle 77 is fitted a drive wheel 78 and to the upper end thereof is attached a bobbin (not shown). The end of the other arm of the rockable lever 75 is tapered to be engageable with a forked portion 700 formed at the upper end of the actu ating lever 70. When said lever 70 rotates clockwise of FIGS. 2 and 14 (upward in FIG. 5), the rockable lever 75 rotates counterclockwise of FIG. 4 to detach the drive wheel 78 from the end face 14d of the rotary member 14. Conversely where the bobbin winding actuating lever 70 makes a counterclockwise rotation, the rockable lever turns clockwise of FIG. 5 to press the drive wheel 78 against the end face 14d of the rotary member 14.

There will now be described the parts of the flywheel 18 by reference to FIGS. 6 to 8. At the flange 17a of the shaft collar 17 is formed a notch 17b. A pin 79 is fixed to the flywheel 18 so as to be disposed in said notch 17b. To said pin 79 is rotatably fitted one end of a first link 80 curved through a peripheral angle of substantially 90. To the other end of said first link 80 is rotatably fitted by a pin 82 one end of a second link 81 curved through a peripheral angle of substantially 90. The other end of said second link 81 is rotatably fitted by a pin 83 to the flange 17a of the shaft collar 17. At one end of the first link 80 is formed a spring holder 80a. Between said spring holder 80a and pin 22 is stretched an extension spring 84 normally to render the flywheel 18 rotatable clockwise of FIGS. 2 and 8, thereby engaging the pin 79 with the inner clockwise side of the notch 17b of the shaft collar 17. Under this condition, the first and

second links

80 and 81, as shown in FIG. 8, present a semicircular form with substantially the same radius as the flange 17a of the shaft collar 17.

When the arm shaft 12 of the sewing machine is brought to rest with the engagement portion 56b of the auxiliary engagement strip 56 of the stop lever 50 engaged with the projecting end b of the spiral spring 20, then the edge of the intermediate part of the second link 81 approaches the side edge of the projecting end of the pin 55 erected on the stop lever 50. Referring to FIG. 1, numeral 85 denotes the cover of the aforementioned mechanism.

There will now be described by reference to FIG. 9 the electrical circuit of the sewing machine of this invention.

Power supply terminals

86 and 87 are connected to a single phase A.C. source of, for example, 100 volts through a plug 9 (FIG. 1 Between the

terminals

86 and 87 is connected a series circuit consisting of a controller switch 88 interlockingly operable with the controller 8 (FIG. 1) depressed by an operator and the electromagnetic solenoid 36. One power supply terminal 86 is connected to a control bus 89 through the switch 30 and the other power supply terminal 87 is directly connected to a control bus 90. Though normally open, the controller switch 88 is closed when the operator depresses the controller 8 to start the sewing machine. Between the

control buses

89 and 90 is connected a series circuit consisting of a thyristor or silicon controlled rectifier (SCR) 91 of the indicated polarity and a motor 92, for example, a series coil A.C. rectifier type motor including field windings 92F and armature winding 92A. This motor 92 drives the rotary member 14 through, for example, the previously mentioned V- belt 16. Further between said

buses

89 and 90 is connected a series circuit including a protective resistor 93, variable resistor 94, fixed low speed setting resistor 95 and diode 96 of the indicated polarity. Parallel with a series circuit consisting of said

resistors

94 and 95 is connected a surge absorption capacitor 97 to form a speed setting circuit 98. The movable element 94a of the variable resistor 94 is connected to the gate of the thyristor 91 through a diode 99 of the indicated polarity. Between the gate and cathode of said thyristor 91 is connected a parallel circuit consisting of a bias resistor 100 and surge absorption capacitor 101. Referring to FIG. 9, numeral 102 is a surge absorption capacitor connected between the

buses

89 and 90.

There will now be described the operation of the sewing machine of this invention arranged as described above FIGS. 2 to 8 (excluding FIG. 6) indicate the rest position of said sewing machine. Under this condition, the stop lever 50 is urged counterclockwise of FIG. 2 by the coil spring 58 to cause the engagement portion 56b of the auxiliary engagement strip 56 to be pressed against the projecting end 20b of the spiral spring 20, thereby disconnecting the rotary member 14 from the arm shaft 12. The intermediate lever 44 is urged clockwise of FIG. 4 by the coil spring 48, causing the restraining lever 46 to rotate in the same direction with the engagement pawl 46a of said lever 46 engaged with the annular groove of the rotary member 14. The plunger 36a of the electromagnetic solenoid 36 is brought to its uppermost position by the extension spring 39, causing the actuating lever 32 to be urged counterclockwise of FIG. 2 to a maximum extent. The rockable lever 40 connected to said actuating lever 32 through the pin 42 is also rotated counterclockwise of FIG. 2 to a maximum extent. Under this condition, the pin 43 erected on the rockable lever 40 is positioned at a substantially middle point of the elongate hole 29e of the switch operating lever 29. Of course, said switch operating lever 29 is lifted uppermost by the extension spring 31. Where the arm shaft 12 stands at rest under the aforementioned condition, (with the projecting end 201) of the spiral spring 20 pressed against the engagement portion 56b of the auxiliary engagement strip 56 of the stop lever 50), then the needle bar 6 and in consequence the needle 6 reciprocated by the arm shaft 12 are lifted uppermost due to the relative position of the projecting end 20b and the opposite end 20a of the spiral spring 20.

There will now be described the operation of the sewing machine of this invention for the various applications for which it is intended.

1. Normal stitching FIGS. 2, 10 and 14 present the relative positions of the cams 61 to 63 when the selection knob is operated for normal stitching (which is effected by setting the mark NS shown in the front face of the knob 59 at the marker 10 indicated on the front side of the cover 85). Under the rest position of the sewing machine shown in FIG. 2, the edge of the supporting lever 34 contacts the first cam plane 61a of the locating cam 61 to cause the actuating lever 32 to make a maximum movement to the left side of FIG. 2, that is, to take the extreme left position where the right inner wall of the elongate hole 32d closely approaches the pin 42. Under this condition, the engagement portion 52a of the engagement member 52 is engaged from above with the first engagement portion 50a of the stop lever 50 and, as illustrated in FIG. 4, the lug portion 32b of the actuating lever 32 faces from above the contact portion 44a of the intermediate lever 44. The engagement portion 68a of the notch pin 68 is inserted into the first depression 62c of the notch cam 62, thereby defining the position of the cams 61 to 63. The actuating lever 70 is rotated clockwise of FIG. 2 to a maximum extent by having its underside pressed against the first cam plane 62a of the notch cam 62, thereby preventing the drive wheel 78 from contacting the end face 14d of the rotary member 14 (FIG.

When, under the aforementioned condition, the controller is depressed to close the controller switch 88 for the start of the sewing machine, then the electromagnetic solenoid 36 is energized through the controller switch 88 to have its plunger 36a pulled downward, thereby causing the actuating lever 32 to rotate clockwise of FIG. 2. As the result, the rockable lever 40 rotates in the same direction through the pin 42 to have its engagement portion 40a engaged with the first depression 63a of the lock cam 63, thereby obstructing the working of the selection knob 59 during the operation of the sewing machine. Rotation of said rockable lever 40 causes its pin 43 to engage the lower inner wall of the elongate hole 2% of the switch operating lever 29 to pull it down. Accordingly, the switch operating lever 29 is brought to its lowermost position against the force of the extension spring 31 to cause its shoulder portion 29d to depress the actuator 30a, thereby 0105- I ing the switch 30 (FIGS. and 14). The closing ofsaid switch introduces current through the speed setting circuit 98 to supply the thyristor 91 with an ignition signal, thereby starting the drive of the motor 92. When the actuating lever 32 rotates clockwise of FIG. 2, the stop lever 50 whose first engagement portion 50a is pressed against the engagement portion 52a of the engagement member 52 also rotates clockwise of FIG. 2 against the force of the coil spring 58, thereby disengaging the projecting end 20b of the spiral spring 20 from the engagement portion 56b of the auxiliary engagement strip 56. Thus, the rotary member 14 driven by the motor 92 is connected to the arm shaft 12 by the action of the spiral spring 20 with the resultant rotation of the latter, thereby starting the normal continuous stitching. Rotation of the actuating lever 32 causes its lug portion 32b to depress the contact portion 440 of the intermediate lever 44. Accordingly, the intermediate lever'44 and the restraining lever 46 rotatably fitted thereto rotate counterclockwise of FIG. 4 to disengage the engagement pawl 46a of said restraining lever 46 from the annular groove 140 of the rotary member 14. Upon said disengagement, the restraining lever 46 is rapidly rotated counterclockwise of FIG. 2 by the coil spring 49, causing its engagement pawl 46a to be pressed against the side wall of the boss 14a of the rotary member 14 with the resultant stop of the restraining lever 46. During the depression of the controller, the lug portion 32b of the actuating lever 32 remains engaged with the contact portion 44a of the intermediate lever 44, keeping the engagement pawl 46a of the restraining lever 46 pressed against the boss 14a of the rotary member 14. Rotation of the restraining lever 46 causes its engagement portion 46b to be moved upward for contact with the engagement portion 29c of the switch operating lever 29 and the second engagement portion 50b of the stop lever 50 (FIG. 10).

While normal stitching is generally conducted in the aforementioned manner, the speed of the motor 92, or sewing may be adjusted by changing the manner in which the controller is depressed, because the movable element 94a of the variable resistor 94 of the speed setting circuit 98 is made to move according to the force of said depression during normal stitching.

When the controller is released from depression upon completion of sewing to bring the sewing machine to rest, then the controller switch 88 is opened to shut off supply of current to the electromagnetic solenoid 36, thereby causing its plunger 36a to be lifted to its uppermost position by the extension spring 39, and also the actuating lever 32 to return to its original position by rotating counterclockwise of FIG. 2. As the result, the rockable lever 40 and stop lever 50 are also brought back to the original position by rotating in the same direction. However, the switch operating lever 29 and stop lever cannot regain the original position, because their

engagement portions

290 and 50b still remain engaged with the engagement portion 46b of the restraining lever 46.

The thyristor 91 is supplied with an ignition signal determined by the low speed setting resistor 95 of the speed setting circuit 98 to cause the motor 92 to be driven at a predetermined low speed. The arm shaft 12 which is still connected to the rotary member 14 at this time makes a slow rotation. Since the return of the actuating lever 32 disengages the lug portion 32b of the actuating lever 32 from the contact portion 44a of the intermediate lever 44, the intermediate lever 44 and the restraining lever 46 to be inserted into the initial portion clockwise of FIG. 4, thereby causing the engagement pawl 46a of the actuating lever 46 to be inserted into the initial portion of the spiral groove 14b of the rotary member 14. Upon said insertion, the engagement pawl 46a of the restraining lever 46 travels through the spiral groove 14b toward the periphery of the rotary member 14 as the result of its rotation, so that the restraining lever 46 rotates clockwise of FIG. 10. Therefore, the engagement portion 46b of the lever 46 so moves as to be disengaged from the

engagement portions

290 and 50b of the switch operating lever 29 and stop lever 50. When the rotary member 14 makes substantially two rotations from the time when the en-

Claims

1. A sewing machine comprising: a frame, an arm shaft rotatably mounted on the frame, an electric motor for driving the arm shaft, circuit means including electrical components to provide variable drive-energy for said motor, a manually depressible controller for regulating the speed of said motor by controlling said electrical components, clutch means for drivingly connecting said motor to said arm shaft, stop means including: a stop member connected to the arm shaft for rotation therewith and having a stop portion, and a stop lever mounted on the frame to move between an operative position in engagement with the stop portion of the stop member and an inoperative position out of engagement with said stop portion of the stop member, urging means for biassing said stop lever in the operative position, said clutch means being adapted to release the driving connection between said motor and said arm shaft upon engagement of said stop lever with the stop portion of said stop member, said stop means being adapted to stop the arm shaft at a predetermined angular position thereof upon engagement of said stop lever with the stop portion of said stop member, actuating means operably interconnected to said stop means and operative to move the stop lever to the inoperative position against the action of said urging means upon depression of said controller and to hold said stop lever in the inoperative position during the depression of said controller, fixed low speed drive means including said motor and effective responsive to relaxation of said controller for driving said arm shaft at a fixed low speed, and restraining means operative responsive to relaxation of said controller for mechanically holding to said stop lever in the inoperative position during a few revolutions of the arm shaft after relaxation of said controller, whereby when the controller is relaxed, said arm shaft is driven at the low speed during a few revolutions thereof while the stop lever is mechanically held in the inoperative position by the operation of the restraining means, subsequently said stop lever is moved to the operative position from the inoperative position, and when said stop lever engages with the stop portion of the stop member, the driving connection through the clutch means is released and the arm shaft is stopped in the predetermined angular position thereof.

2. A sewing machine according to claim 1, wherein said restraining means comprises: a rotary member rotatably mounted around the arm shaft and drivingly connected to said motor, said rotary member having a spiral groove and a circular groove communicated with the terminal portion of said spiral groove, and a restraining lever pivotally mounted on the frame to engage with said groove at one end and to engage with said stop lever at the other end, said restraining lever being adapted to engage at one end with a begining portion of said spiral groove in response to relaxation of the controller and to simultaneously engage at the other end with the stop lever, whereby said stop lever is held in the inoperative position by the restraining lever until the restraining lever is disengaged with the stop lever by the pivotal movement imparted to said restraining lever upon rotation of said spiral groove of the rotary member.

3. A sewing machine according to claim 1, wherein said stop member is adapted to alter an angular position of the stop portion by 180* relative to the arm shaft, whereby the predetermined angular stop position of the arm shaft is shiftable by 180* .

4. A sewing machine according to claim 1, wherein said fixed low speed drive means includes a fixed low speed setting resistance disposed in said circuit means, said fixed low speed setting resistance being effective responsive to relaxation of said controller for providing low speed drive energy for said motor.

5. A sewing machine according to claim 4, wherein said circuit means includes switch means adapted to be closed in response to depression of said controller and to be opened late in stopping of the arm shaft in the predetermined angular position after relaxation of said controller.

6. A sewing machine comprising: a frame, an arm shaft rotatably mounted on the frame, an electric motor for driving the arm shaft, circuit means including electrical components to provide variable drive energy for said motor, a manually depressible controller for regulating the speed of said motor by controlling said electrical components, a driving element rotatably mounted around said arm shaft and connected to said motor, a driven element secured to said arm shaft, a clutch for drivingly connecting or disconnecting said driving element to said driven element, said clutch being connected to said driven element and having a stop portion, a stop lever mounted on the frame to move between an operative position in engagement with the stop portion of said clutch and an inoperative position out of engagement with said stop portion of the clutch, urging means for normally biassing said stop lever in the operative position, said clutch being constructed and arranged such that when said stop lever engages with the stop portion of the clutch the driving connection between the driven element is released and the arm shaft is stopped in a predetermined angular position thereof, actuating means operably connected to said stop lever and operative to move the stop lever to the inoperative position against the action of said urging means upon depression of said controller and to hold said stop lever in the inoperative position during the depression of said controller, fixed low speed drive means including said motor and effective responsive to relaxation of said controller for driving said driving element at a fixed low speed, and restraining means operative responsive to relaxation of said controller for mechanically holding said stop lever in the inoperative position against the action of said urging means during a few revolution of the arm shaft after relaxation of said controller, whereby when the controller is relaxed, said arm shaft is driven at the low speed during a few revolutions thereof while the stop lever is mechanically held in the inoperative position by the operation of the restraining means, subsequently said stop lever is moved to the operative position from the inoperative position, and when said stop lever engages with the stop portion of the clutch, the driving connection through the clutch is released and the arm shaft is stopped at the predetermined angular position.

7. A sewing machine comprising: a frame, an arm shaft rotatably mounted on the frame, an electric motor to drive the arm shaft, circuit means including a variable resistance and a fixed low speed setting resistance and providing drive energy for said motor, a manually depressible controller for regulating the speed of said motor by controlling said variable resistance, said circuit means being adapted to provide low speed drive energy for said motor through the fixed low speed setting resistance upon relaxation of said controller, a driving element rotatably mounted around said arm shaft and connected to said motor, and having a cylindrical portion, a driven element secured to said arm shaft, a clutch comprising a spiral spring wrapped around the cylindrical portion of said driving element for drivingly connecting or disconnecting said driving element to said driven element, said spiral spring haVing one end connected to said driven element and the other end radially projecting, a stop lever pivotally mounted on the frame to move between an operative position in engagement with the projecting end of said spiral spring and an inoperative position out of engagement with said projecting end of the spiral spring, urging means for biassing said stop lever in the operative position, said clutch being adapted to release the driving connection between the driving element and the driven element upon engagement of said stop lever with said projecting end of the spiral spring, said spiral spring being constructed and arranged such that when said stop lever engages with the projecting end of the spiral spring said arm shaft is stopped at a predetermined angular position thereof, actuating means operably connected to said stop lever and operative to move the stop lever to the inoperative position upon depression of said controller and to hold said stop lever in the inoperative position during the depression of said controller, and restraining means operative responsive to relaxation of said controller for mechanically holding said stop lever in the inoperative position during a few revolutions of the arm shaft after relaxation of said controller, whereby when the controller is relaxed, said arm shaft is driven at the low speed during a few revolutions while the stop lever is held in the inoperative position against the action of the urging means by the restraining means, subsequently said stop lever is moved to the operative position from said inoperative position, and when said stop lever engages with the projecting end of the spiral spring, this driving connection through the clutch is released, and the arm shaft is stopped at the predetermined angular position thereof.

8. A sewing machine comprising: a frame, an arm shaft rotatably mounted on the frame, an electric motor for driving the arm shaft, circuit means including electrical components to provide variable drive energy for said motor, a manually depressible controller for regulating the speed of said motor by controlling said electrical components, clutch means for drivingly connecting said motor to said arm shaft, stop means including: a stop member connected to the arm shaft for rotation therewith and having a stop portion, and a stop lever mounted on the frame to move between an operative position in engagement with the stop portions of said stop member and an inoperative position out of engagement with said stop portion of the stop member, urging means for biassing said stop lever in the operative position, said clutch means being adapted to release the driving connection between said motor and said arm shaft upon engagement of said stop lever with the stop portion of said stop member, said stop means being adapted to stop the arm shaft at a predetermined angular position thereof upon engagement of said lever with the stop portion of said stop member, actuating means operably interconnected to said stop means and adapted to perform a first operation to move the stop lever to the inoperative position against the action of said urging means upon depression of said controller and a second operation to hold the stop lever in the inoperative position during the depression of said controller, fixed low speed drive means including said motor and effective responsive to relaxation of said controller for driving said arm shaft at a fixed low speed, restraining means operative responsive to relaxation of said controller for mechanically holding said stop lever in the inoperative position during a few revolutions of the arm shaft after relaxation of said controller, and manual contral means for controlling the operations of said acturting means and the operation of said restraining means, said manual control means being adapted to be set selectively either in a first position to enable the operations of saId actuating means and said restraining means or in a second position to enable only the first operation of the actuating means and to disable the second operation of the actuating means and the operation of the restraining means, whereby when the controller is depressed in the second position of said manual control means, the stop lever is moved to the inoperative position, and instantly said stop lever is returned to the operative position by the action of said urging means in spite of a succession of depressions of said controller, so that the arm shaft is stopped at a predetermined angular position thereof after one revolution thereof.

9. A sewing machine according to claim 8, wherein said actuating means comprises: a supporting member movably mounted on the frame, an actuating lever pivotally mounted on said supporting member and operably engaging with the stop lever, said actuating lever being adapted to permit a longitudinal movement thereof upon movement of said supporting member, and an operating member operably connected to said actuating lever and operative responsive to depression of said controller for swinging said actuating lever and moving said stop lever to the inoperative position, said manual control means being operably interconnected to said actuating means and being adapted to shift a pivotal point of said actuating lever by the movement of the supporting member upon selection of the manual control means.

10. A sewing machine according to claim 8, wherein said manual control means is adapted to disable the operation of said fixed low speed drive means in the second position of the manual control means.

11. A sewing machine comprising: a frame, an arm shaft rotatably mounted on the frame, an electric motor for driving the arm shaft, circuit means including electrical components to provide variable drive energy for said motor, a manually depressible controller for regulating the speed of said motor by controlling said electrical components, a driving element rotatably mounted around said arm shaft and connected to said motor, a driven element secured to said arm shaft, a clutch for drivingly connecting or disconnecting said driving element to said driven element, said clutch being connected to said driven element and having a stop portion, a stop lever mounted on the frame to move between an operative position in engagement with the stop portion of said clutch and an inoperative position out of engagement with said stop portion of the clutch, urging means for normally biassing said stop lever in the operative position, said clutch being constructed and arranged such that when said stop lever engages with the stop portion of the clutch the driving connection between the driving element and the driven element is released and the arm shaft is stopped in a predetermined angular position thereof, actuating means operably connected to said stop lever and adapted to perform a first operation to move the stop lever to the inoperative position against the action of said urging means upon depression of said controller and a second operation to hold the stop lever in the inoperative position during the depression of said controller, fixed low speed drive means including said motor and effective responsive to relaxation of said controller for driving said driving element at a fixed low speed, restraining means operative responsive to relaxation of said controller for mechanically holding said stop lever in the inoperative position against the action of said urging means during a few revolutions of the arm shaft after relaxation of said controller, and manual control means for controlling the operations of said actuating means and said restraining means, said manual control means being adapted to be set selectively either in a first position to enable the operations of said actuating means and said restraining means or in a second position to enable only the first operation of the actuating means and to disable the second operation of the actuating means and the operation of the restraining means, whereby when the controller is depressed in the second position of said manual control means, the stop lever is moved to the inoperative position, and instantly said stop lever is returned to the operative position by the action of said urging means in spite of a succession of depressions of said controller, so that the arm shaft is stopped at the predetermined angular positon therof after one revolution thereof.

12. A sewing machine comprising: a frame, an arm shaft rotatably mounted on the frame, an electric motor for driving the arm shaft, circuit means including electrical components to provide variable drive energy for said motor, a manually depressible controller for regulating the speed of said motor by controlling said electrical components, clutch means for drivingly connecting said motor to said arm shaft, said clutch means including a driving element rotatably mounted around said arm shaft and connected to said motor, stop means including: a stop member connected to the arm shaft for rotation therewith and having a stop portion, and a stop lever mounted on the frame to move between an operative position in engagement with the stop portion of said stop member and an inoperative position out of engagement with the stop portion of the stop member, urging means for biassing said stop lever in the operative position, said clutch means being adapted to release the driving connection between said motor and said arm shaft upon engagement of said stop lever with the stop portion of said stop member, said stop means being adapted to stop the arm shaft at a predetermined angular position thereof upon engagement of said stop lever with the stop portion of said stop member, actuating means operably interconnected to said stop means and operative to move the stop lever to the inoperative position against the action of said urging means upon depression of said controller and to hold said stop lever in the inoperative position during the depression thereof; fixed low speed drive means including said motor and effective responsive to relaxation of said controller for driving said arm shaft at a fixed low speed, restraining means operative responsive to relaxation of said controller for mechanically holding said stop lever in the inoperative position during a few revolutions of the arm shaft after relaxation of said controller, manual control means for controlling operations of both said actuating means and saId restraining means, said manual control means being adapted to be set selectively either in an operative position to disable operations of both said actuating means and said restraining means or in an inoperative position to enable said both operations thereof, and a bobbin winder mounted on the frame adjacent said driving element to be selectively shiftable into and out of driving contact with said driving element, whereby when the controller is depressed in the operative position of said manual control means, the stop lever is not moved to the inoperative position, the driving connection through the clutch means is not established and only the driving element is driven, while the arm shaft is stopping in the predetermined angular position, so that the bobbin winder is operated by shifting thereof into driving contact with said driving element.

13. A sewing machine according to claim 12, wherein said bobbin winder is operably connected to the manual control means through a linkage and adapted to be automatically shifted into or out of driving contact with said driving element in response to selection of said manual control means in the operative position or in the inoperative position thereof respectively.

14. A sewing machine according to claim 12, wherein said manual control means is adapted to disable the operation of saiD fixed low speed drive means in the operative position of manual control means.

15. A sewing machine comprising: a frame, an armshaft rotatably mounted on the frame, an electric motor for driving the arm shaft, circuit means including electrical components to provide variable drive energy for said motor, a manually depressible controller for regulating the speed of said motor by controlling said electrical components, a driving element rotatably mounted around said arm shaft and connected to said motor, a driven element secured to said arm shaft, a clutch for drivingly connecting or disconnecting said driving element to said driven element, said clutch being connected to said driven element and having a stop portion, a stop lever mounted on the frame to move between an operative position in engagement with the stop portion of said clutch and an inoperative position out of engagement with said stop portion of the clutch, urging means for normally biassing said stop lever in the operative position, said clutch being constructed and arranged such that when said stop lever engages with the stop portion of the cluch the driving connection between the driving element and the driven element is released and the arm shaft is stopped at a predetermined angular position thereof, actuating means operably connected to said stop lever and operative to move the stop lever to the inoperative position against the action of said urging means upon depression of said controller and to hold said stop lever in the inoperative position during the depression of said controller, fixed low speed drive means including said motor and effective responsive to relaxation of said controller for driving said driving element at a fixed low speed, restraining means operative responsive to relaxation of said controller for mechanically holding said stop lever in the inoperative position against the action of said urging means during a few revolutions of the arm shaft after relaxation of said controller, manual control means for controlling the operations of both said actuating means and said restraining means, said manual control means being adapted to be set selectively either in an operative position to disable operations both said actuating means and said restraining means or in an inoperative position to enable said both operations thereof, and a bobbin winder mounted on the frame adjacent said driving element to be selectively shiftable into and out of driving contact with said driving element, whereby when the controller is depressed in the operative position of said manual control means, the stop lever is not moved to the inoperative position, the driving connection through the clutch is not established and only the driving element is driven, while the arm shaft is stopping in the predetermined angular position, so that the bobbin winder is operated by shifting thereof into driving contact with said driving element.

16. A sewing machine according to claim 15, further comprising: a bobbin winder mounted on the frame, and third means for operating the bobbin winder for stopping the arm shaft at the predetermined angular position thereof by depression of the controller.

17. A sewing machine comprising: a frame, an arm shaft rotatably mounted on the frame, an electric motor for driving the arm shaft, circuit means including electrical components to provide variable drive energy for said motor, a manually depressible controller for regulating the speed of said motor by controlling said electrical components, a driving element rotatably mounted around said arm shaft and connected to said motor, a driven element secured to said arm shaft, a clutch for drivingly connecting or disconnecting said driving element to said driven element, a bobbin winder mounted on the frame adjacent said driving element to be selectively shiftable into and out of driving conTact with the driving element, said clutch being connected to said driven element and having a stop portion, a stop lever mounted on the frame to move between an operative position in engagement with the stop portion of said clutch and an inoperative position out of engagement with said stop portion of the clutch, urging means for normally biassing said stop lever in the operative position, said clutch being constructed and arranged such that when said stop lever engages with the stop portion of the clutch the driving connection between the driving element and the driven element is released and the arm shaft is stopped at a predetermined angular position thereof, actuating means operably connected to said stop lever and adapted to perform a first operation to move the stop lever to the inoperative position against the action of said urging means upon depression of said controller and a second operation to hold the stop lever in the inoperative position during the depression of said controller, fixed low speed drive means including said motor and effective responsive to relaxation of said controller for driving said driving element at a fixed low speed, restraining means operative responsive to relaxation of said controller for mechanically holding said stop lever in the inoperative position against the action of said urging means during a few revolutions of the arm shaft after relaxation of said controller, and manual control means for controlling the operations of said actuating means and said restraining means, said manual control means being adapted to be set selectively in three different positions, the first position to enable the operations of the actuating means and the restraining means, the second position to enable only the first operation of the actuating means and to disable the second operation of the actuating means and the operation of the restraining means, and the third position to disable said all operations thereof, whereby in the first position of said manual control means the arm shaft is continuously driven during the depression of said controller and is stopped at the predetermined angular position thereof after relaxation of said controller, in the second position of said manual control means the arm shaft is stopped at the predetermined angular position thereof after one revolution of the arm shaft in spite of a succession of the depressions of said controller, and in the third position of said manual control means the arm shaft is not driven in spite of the depression of said controller and only the driving element is driven at that time.

18. A sewing machine comprising: a frame, an arm shaft rotatably mounted on the frame, an electric motor for driving the arm shaft, circuit means including variable speed-setting components, a manually depressible controller for regulating the speed of said motor by controlling said speed-setting components, and a needle positioning device for stopping the arm shaft at a predetermined angular position thereof, said needle positioning device comprising: first means operative responsive to relaxation of said controller to stop the arm shaft at the predetermined angular position thereof after relaxation of the controller, second means operative in response to depression of said controller to stop the arm shaft at the predetermined angular position thereof after one revolution of the arm shaft even when the controller is depressed, and manual control means operated by a selection knob operative outside the frame prior to depression of said controller, said manual control means being adapted to be set selectively either in a first position to effect the operation of said first means or in a second position to effect the operation of said second means, whereby said arm shaft is subject to different drive control according to the selected position of the manual control means even though the controllEr may be continuously depressed in the same manner.

19. A sewing machine according to claim 18 further comprising a bobbin winder mounted on the frame, and wherein said needle positioning device further comprises third means operative to actuate the bobbin winder with its shaft stopped at its predetermined angular position by depression of the controller, said manual control means being further adapted to be set selectively in a third position to effect the operation of the third means by the selection knob.