US3889615A - Safety device for a sewing machine - Google Patents

Abstract

A sewing machine is provided with a safety device which does not permit a high speed stitching operation to be performed during the performance of a cutting operation. The cutting mechanism is actuated by means of a knee-operated switch for the performance of the cutting operation and simultaneously therewith, a solenoid-actuated detent is also activated so as to prevent a mechanical connection from being attained between the primary power source of the machine and the machine drive shaft. In this manner, power from the primary power source is not conducted to the drive shaft during the cutting operation and consequently the stitching operation is not able to be performed.

Description

United States Patent Uozake et a1.

Inventors: Seizo Uozake, Toyota; Hitoshi Sakashita, Nukata, both of Japan Aisin Seiki Kabushiki Kaisha, Japan May 30, 1974 Assignee:

Filed:

App]. No.:

[30] Foreign Application Priority Data May 30. 1973 Japan 7. 48-61383 US. Cl 112/252; 112/219 A Int. Cl D051) 65/00 Field of Search... 112/122, 130, 219 R, 219 A,

References Cited UNlTED STATES PATENTS 1 1 June 17, 1975 3585.950 6/1971 lto 1. 112/252 X Primary E.raminerWerner H. Schroeder Attorney. Agent, or Firm-Oblon, Fisher. Spivak,

McClelland & Maier [57] ABSTRACT A sewing machine is provided with a safety device which does not permit a high speed stitching operation to be performed during the performance of a cutting operation. The cutting mechanism is actuated by means of a knee-operated switch for the performance of the cutting operation and simultaneously therewith, a solenoid-actuated detent is also activated so as to prevent a mechanical connection from being attained between the primary power source of the machine and the machine drive shaft. In this manner, power from the primary power source is not conducted to the drive shaft during the cutting operation and consequently the stitching operation is not able to be performed.

6 Claims, 15 Drawing Figures SHEET PATENTEDJUH 1 7 I975 FIG.1

PATENTEDJUN 17 ms SHEET FIG.8

PATENTEDJUM 17 1915 3,889,615

n SHEET 9 FIGJL SHEET PATENTEDJUN 17 ms FIGJS SAFETY DEVICE FOR A SEWING MACHINE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to sewing machines within which automatic thread cutting devices are provided, and more particularly to a safety device or mechanism incorporated within the thread cutting device of the sewing machine for reliably and securely actuating the thread cutting device.

2. Description of the Prior Art Conventional sewing machines are known wherein mechanisms are employed and actuated, between stitching operations, whereby upper and lower threads may be automatically caught and severed, by means of the thread holder and cutter device, at a position between the cloth material and the shuttle race. Within a few of such prior art thread cutting devices, safety devices are also provided for reliably actuating the same.

However, such safety devices are usually only actuated at the same time or prior to the performance of the thread cutting operation. Therefore, if the foot pedal or the like is erroneously depressed so as to actuate a stitching operation during a thread cutting operation, the thread cutting device under operation, as well as other component parts of the machine, might be damaged due to the undesired forces suddenly applied thereto as a result of the erroneously actuated stitching components.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an improved sewing machine which incorporates a safety device which obviates the abovementioned drawbacks characteristic of conventional sewing machines.

Another object of the present invention is to provide an improved sewing machine which incorporates a safety device which prevents the high speed actuation of the stitching operation of the machine while a thread cutting operation is being performed.

BRIEF DESCRIPTION OF THE DRAWINGS Various other objects, features, and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description when considered in connection with the accompanying drawings, in which like reference characters designate like or corresponding parts throughout the several views, and wherein:

FIG. I is a front elevation view of a sewing machine incorporating the safety device of the present invention;

FIG. 2 is a bottom view of a thread cutting device incorporated within the sewing machine of FIG. I;

FIG. 3 is a perspective view of the device of FIG. 2;

FIG. 4 is an end view of the device of FIG. 2;

FIG. 5 is a perspective view of a thread tension release mechanism incorporated within the machine of the present invention;

FIG. 6 is an end view, partly in section, of a needle and a needle bar secured to the machine arm;

FIG. 7 is a schematic view of the ratchet wheels of the thread cutting device of the machine of the present invention;

FIG. 8 is a view similar to that of FIG. 4, partly in section and showing however the thread holding operation being initiated;

FIG. 9 is a view similar to that of FIG. 7 showing however the ratchet wheels being engaged;

FIG. 10 is a view similar to that of FIG. 8 showing however the thread holding operation;

FIG. 11 is a view similar to that of FIG. 9 showing however advanced engagement of the ratchet wheels being performed;

FIG. 12 is a view similar to that of FIG. 10, showing however the thread cutting operation being terminated;

FIG. 13 is a view similar to that of FIG. 11, showing however the position of the ratchet wheels corresponding to the operation illustrated within FIG. 12;

FIG. 14 is a cross-sectional view of the safety device constructed according to the present invention and showing its cooperative parts; and

FIG. 15 is a schematic diagram of the electrical circuitry embodied within the safety device of FIG. 14.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, and more particularly to FIGS. 1-9 thereof, the sewing machine of the present invention includes a horizontally disposed arm 44 and a bed 1 upon which the machine is fixedly supported. A frame member 2 is secured to the rear portion of bed 1 by means of screw bolts 3 and 4 and a stepped shaft 6 which is pivotally mounted upon frame member 2 is provided at one end thereof with a stepped portion 9 and a lever member 5. A disc-type setting member 7 is also mounted upon shaft 6 and at the end opposite to that upon which member 5 is mounted, member 7 being fixed thereon by means of a set screw 8 which is adapted to be inserted within a rectangularly configured portion 13 of setting member 7.

The axial displacement of shaft 6 may be prevented by interposing a portion of frame member 2 between the stepped portion 9 of shaft 6 and the setting member 7, as is best shown in FIG. 2, and a coil spring 10 is interposed between the frame member 2 and the setting member 7 and about shaft 6 whereby an arm portion 7a of setting member 7 is, under the influence of the biasing force of spring 10, urged into contact with a stopper pin 11 which is threadedly engaged within the frame member 2. In this manner, the setting member 7, and accordingly, the shaft 6, is prevented from rotating in a counterclockwise direction from the inoperative positions illustrated within FIG. 3.

A first ratchet wheel member 12 is pivotably mounted upon shaft 6 and includes an outer peripheral portion which is partially toothed as illustrated at as shown in FIG. 7 and also includes a partially formed cam surface, and an axially extending recess defining portion 14 within which the rectangular portion 13 of the setting member 7 is longitudinally receivable whereby the first ratchet wheel member 12 is freely slidable upon shaft 6 in the axial direction thereof but is also secured against rotation with respect thereto. In this manner, then, the first ratchet wheel member 12, the setting member 7, and the shaft 6 may be rotated in unison. In conjunction with such structure, it is further seen that another coil spring 20 is similarly interposed between the setting member 7 and the first ratchet wheel member 12 for normally biasing the latter toward the right as seen in FIGS. 2 and 3.

A lever is also slidably mounted upon shaft 6 adjacent to the first ratchet wheel member 12, and at one outer end thereof is provided with a recess 16 within which a plunger 19 is inserted, the latter of which is operatively connected to a first solenoid means 18 through means of an intermittent lever 103. As the first solenoid means 18, as well as a second solenoid means 76, a somewhat detailed description of which appears hereinafter, may be applicable within any conventional solenoid valve mechanism, a detailed description of the construction thereof is hereby omitted, although it is noted that the first solenoid means 18 is secured to frame member 2 by means of a plurality of bolts 17.

Upon energization of the first solenoid means 18, the plunger 19 is moved toward the left as seen in FIGS. 2 and 3 so as to similarly move lever 15 toward the left the movement of which in turn causes the movement or displacement of the first ratchet wheel member 12 toward the left so as to overcome the biasing force of coil spring 20.

A cable member 22 is passed through a through-hole 21 provided within the other end lever 15 and is fixed relative thereto by means of a pair of stoppers 23. The cable member 22 is additionally slidably movable within an outer cable member 102 one end of which is fixed to the intermittent lever 103 by means of a clip 104.

Another shaft 24 disposed parallel to shaft 6 is rotatably supported upon bed 1 through means of a bushing 25 which is press-fitted within bed 1, and a holder 26 is rotatably mounted upon one end of shaft 24. A stop ring 27 is provided so as to prevent holder 26 from undergoing any axial displacement relative to shaft 24, and the other end of shaft 24 is operatively connected to a hand wheel 84 (See FIG. I) through means of a link, not shown, provided within the arm 44. Holder 26 is relatively rotatably connected to lever portion 5 of shaft 6 through means of a link member 28 one end of which is secured to holder 26 by means of a stepped, threaded bolt 29, while the other end thereof is similarly secured to lever portion 5 by means of another stepped threaded bolt 30.

A stationary blade member 32 and a tension thread guide 33 are fixedly secured to bed 1 by means of a screw bolt 31 and a presser foot 35 is similarly fixed to holder 26 by means of a screw bolt 34 so as to face stationary blade member 32 whereby a first blade portion 41 of member 32 and a second blade portion 40 (See FIG. 8) of presser foot 35 may be pivoted together so as to overlap an area with respect to each other and thereby coact together in the manner of a scissors so as to perform a thread cutting operation. The arcuate portion of tension thread guide 33 is interposed between a shuttle race 36 and presser foot 35 and is positioned coaxially therewith, and an aperture 97 is provided within the tip portion of tension thread guide 33 for providing a passageway for thread to be passed therethrough. The presser foot 35 is seen to serially comprise a horn 37, a thread guard 38, a groove or slot 39, and the blade 40.

Still referring to FIGS. 2 and 3, a second ratchet wheel member 42 fixedly secured upon shaft 24 by means of a threaded bolt 43 comprises a toothed portion 98 (Sec FIG. 7) and an outwardly extending cam surface 92 the diameter of which is gradually increased and subsequently decreased to an amount less than that of the toothed portion 98. Ratchet wheel 42 is thus oscillatingly rotated together with shaft 24 during a normal stitching operation, however upon the performance of a thread cutting operation whereby the first solenoid means 18 is energized, the first ratchet wheel member 12 will be move along shaft 6 to a position so as to be engageable with the second ratchet wheel 42. A switch MD provided upon bed 1 is maintained within its OFF condition unless the holder 26 is rotated by means of the lever portion 5 of shaft 6, that is, the switch MD is actuated only when a thread cutting operation is required.

As may be especially seen within FIG. 5, a tension release member 45 and a rotatable member 46 are relatively rotatably connected to each other by means of a pin 47 secured to the arm 44 of the machine. The tension release member 45 has a cam surface 48 at one end thereof and upon rotation of tension release member 45, a pin rod 49 which is connected to a wellknown thread tension regulator 50 a detailed construction of which is hereby omitted, is forced to ride over the cam surface 48 of tension release member 45 so as to push the pin rod 49 toward the regulator 50 whereby the tension within the upper thread may be released by means of the operation of regulator 50.

The other end of outer cable member 102 is fixed to arm 44 by appropriate securing means, not shown, and since the inner cable member 22 is at one end thereof connected to tension release member 45 while the other end thereof is fixed to lever 15 as seen in FIG. 3, upon energization of the first solenoid means 18 and therefore upon the performance of a thread cutting operation, the tension release member 45 is rotated about pin 47 so as to release the tension within the upper thread as a result of the operation of regulator 50. Upon tie-energization of the first solenoid means 18, the tension release member 45 will be returned to the position illustrated within FIG. 5 by means of the biasing force of a spring 51 interposed between the upper end of tension release member 45 and the outer cable member 102.

In connection with the tension release operation, a conventional presser foot lifting operation will now be briefly explained. A lifting plate 52 is operatively connected to a conventional presser foot lifting member, partially shown but not numbered, at one end thereof while a pin 53 is provided upon the lifting plate 52 near the other end thereof and is adapted to be loosely disposed within a bifurcated or forked portion 54 of the rotatable member 46. Upon raising the plate 52 by means of the presser foot lifting member the rotatable member 46 is consequently rotated in the clockwise direction as seen in FIG. 5 whereby the same will come into contact with a detent 55 provided upon tension release member 45 which thereby serves to operate the regulator 50 so as to release the upper tensioned thread. It is noted that this operation is performed independently of the energization and de-energization of the first solenoid means 18.

Referring more particularly to FIG. 6, a timing mark is stamped upon a needle bar 94 at a predetermined position thereof, such position being determined such that when the mark 95 is aligned with the under side or bottom surface of the needle bar metal support 96, as seen in FIG. 6, the timing is set such that the needle bar is approximately 55 ahead of the upper dead center position.

Turning now to FIGS. 1 and 14, a clutch motor housing 57 is suitably secured beneath the sewing machine table 56 and within housing 57 there is provided a motor assembly 59, a first flywheel 58 connected to one end of the motor assembly drive shaft, not numbered, a clutch disc 60, and a second flywheel 63, all of which are serially arranged from left to right as seen in FIG. 14, it therefore being noted that the outer surfaces of the clutch disc 60 are opposed to the first and second flywheels 58 and 63. An arm lever 62 is pivotally mounted upon the housing 57 by means of a pivot pin 61 and the clutch disc 60 is operatively connected to arm lever 62 whereby disc 60 may undergo sliding movement in response to rotation of lever 62. A return spring 64 is interposed between a support member, not numbered, of the housing 57 and a stop member, also not numbered, of the arm lever 62 so as to normally bias the latter to its inoperative position whereby the clutch disc 60 within the housing 57 will normally be in contact with the second flywheel 63 but not in contact with flywheel 58 whereby a driving torque from the motor 59 is normally not transmitted to a pulley 72 which is associated with the main drive shaft of the machine, not shown, through means of pulley 84 and belt 73.

The second flywheel 63 is integrally formed with a worm wheel 66 the latter of which is intermeshed with a worm portion 65 of a drive shaft, not numbered, of an auxiliary motor 67. The lower end of the drive shaft, not numbered, is operatively associated with a brake coil 69 and a brake disc 68, the working surfaces of members 68 and 69 being disposed in opposed relation with respect to each other.

The arm lever 62 is operatively connected to a foot pedal 71 through means of a connecting rod 70 and upon depression of pedal 71 the arm lever 62 is rotated in the counterclockwise direction so as to disengage the clutch disc 60 from the second flywheel 63 and alternatively, to engage disc 60 with the first flywheel 58. In this manner, the drive torque from the motor 59 is able to be transmitted to the hand pulley wheel 85 through means of the first flywheel 58, clutch disc 60, pulley 72, and pulley belt 73 for driving the sewing machine in the well-known fashion, the hand wheel 84 of course being operatively connected to the main drive shaft, not shown, provided within the arm 44.

At the other end of arm lever 62 there is provided a supporting plate 101 upon which hook 74, the second solenoid means 76, and a switch MC are mounted. The hook 74 is pivotally mounted upon the plate 101 by means of a pivot pin 75 and is also connected to the second solenoid means 76 by means of a link member 77. A coil spring 79 is interposed between the link 77 and the second solenoid means 76 so as to normally bias the hook 74 toward the left as seen in FIG. 14, and detent 78 is secured to housing 57 so as to be opposed to a bent portion 80 of the hook 74. The detent '78 comprises a hooked portion 81 and a planar portion 83, and upon energization of the second solenoid means 76, the hook 74 is rotated in the clockwise direction pivoting around the pin 75 and overcoming the biasing force of spring 79 so that the bent portion 80 of the book 74 may be engaged with the hook portion 81 of the detent 78 thereby preventing the arm lever 62 from achieving any counterclockwise rotation. The switch MC is to be actuated only after the arm lever 62 has been rotated by means of the pedal 71.

Upon rotation of lever 62 due to the depression of pedal 71, hook 74 is moved downwardly, as seen in FIG. 14, together with lever 62 and under these conditions, if the solenoid 76 is energized, a hook 82, formed at the extremity of the bent portion 80, comes into contact with the planar portion 83 of detent 78 so as to prevent lever 62 from undergoing any further rotation. As noted hereinbefore, the hand wheel 84 is connected to pulley 72 of housing 57 through means of a V- shaped belt 73 so as to selectively transmit the drive torque from either the motor 59 or auxiliary motor 67.

A conventional sensor means 85 is secured to the pulley 84 for generating and transmitting a signal to a control circuit 86 so as to timely actuate the thread cutting operation. As best seen in FIG. 15, the sensor 85 comprises a disc 88 which includes an isolator 87 and is rotatable with the hand wheel 84, and a pair of dia metrically opposed contacts 89 and are positioned in contact with the outer periphery of disc 88 and are secured against rotation therewith. The position of contact 89 is to be approximately located at the top dead center point of a thread take-up lever, not shown, and operatively connected with the main drive shaft of the machine, while the position of contact 90 is to be approximately located at the bottom dead center point of the thread take-up lever.

Relays R1, R2, and R3 respectively actuate switches Rl-1-R1-4, R2-l-R2-4, and R3-1-R3-4 so as to perform the desired ON-OFF switching operations, the relay R1 being operable when the rotational speed of the disc 88 becomes less than approximately 300 R.P.M. and similarly being inoperable when the speed is greater than 300 R.P.M. The switch MA is positioned to the ON po' sition upon rotation of the arm lever 62 as seen in FIG. 14 and the switch MB is positioned to the ON position as a result of a manual pushing action, such as for example may be performed by a knee of the operation when the thread cutting operation is desired. The switch MC is likewise positioned to the ON mode when the safety device is actuated so as to prevent the arm lever 62 from rotating, and the switch MD may be moved to the ON position when the thread cutting operation is initiated. D,, D and D are conventional diodes which permit electric current to flow in only one direction.

When a thread cutting operation is required as a result of the completion of the particular stitching operations, the first solenoid means 18 is energized so as to move the plunger 19 and shift the ratchet wheel 12 to the position at which wheel 12 is disposed opposite ratchet wheel 42 so as to be engageable therewith as is shown in FIG. 7. When the shaft 24, which is actuated by means of the motor 59, is rotated to a position which is approximately 55 ahead of the corresponding top head center position of the needle, then the ratchet wheel 42 will be engaged with the ratchet wheel 12 thereby transmitting the drive torque from the shaft 24 to the shaft 6 thus initiating the thread cutting operation as a result of the rotation of holder 26.

More particularly, when the engagement between the ratchet wheels 12 and 42 attains the condition illus trated within FIG. 9 from that of FIG. 7, then the horn portion 37 of the presser foot 35 catches the upper thread N forcing the same into a loop which is formed within the shuttle race 36 while the thread guard 38 of the presser foot 35 similarly catches and draws the lower thread B from the bobbin case 91. Continuing further, when the engagement between the ratchet wheels 12 and 42 attains the condition illustrated within FIG. 11 from that of FIG. 9 that is, upon engagement between the teeth 98 and 100 being achieved or ended, and simultaneously therewith, the upper thread N is pulled in an upward direction by means of a conventional lever take-up operation, then the upper thread N is caught by means of the presser foot 35 which secures the same within the needle hole so as not to be capableof coming out therefrom while the lower thread B is conducted through the groove or slot 39 within the thread guard 38 of the presser foot 35 together with the upper thread N near the surface of the cloth to be sewn. Accordingly, cutting of the lower thread B is prevented at this stage and consequently, an appropriate length thereof is drawn from the bobbin case 91 in order to prepare for further or subsequent stitching operations after performance of the cutting operation.

As a result of the engagement between the teeth 98 of wheel 12 and the teeth 100 of wheel 42, as is shown in FIG. 9, the blade 40 of the presser foot 35 and the blade 41 of the stationary blade member 32 are caused to rapidly close with respect to each other so that the timing of the thread cutting operation may correspond as closely as possible to the top dead center position of the thread take-up lever, and after the last tooth 93 of the teeth 98 has been disengaged from the teeth 100 of the wheel 42, as is shown in FIG. 11, the tooth 93 of wheel 12 will be in contact with the cam surface 92 of wheel 42 as best seen in FIG. 13, whereby the presser foot 35 will be caused to move slowly so that both the upper and lower threads N and B are assuredly severed.

After the threads have been severed, that is, the engagement between the first and second ratchet wheels 12 and 42 has been released, then the setting member 7, together with the ratchet wheel 12 which has now been disengaged from the ratchet wheel 42, is rotated in the counterclockwise direction, as seen in FIG. 3, due to the biasing force of the coil spring until the arm portion 7A of member 7 makes contact with the stopper pin 11, the presser foot 35 thereby being returned to the original position as shown in FIG. 4. lt should be noted here that the needle aperture 97 of the tension thread guard 33 is provided for reliably securing the upper thread N during the aforenoted operations by inserting the thread N therethrough at the time of performance of the thread take-up operation.

Referring now to the operation of the safety device, when the pedal 71 is disposed within its neutral position, as shown in FIG. 14, the main drive motor 59 and flywheel 58 are rotated together, however the driving torque thereform is not transmitted to the clutch disc 60 as the same is not engaged therewith. At this time, since the switch MA has not been actuated, the auxiliary motor 67 is therefore not rotated, and furthermore, as the brake coil 69 is energized, the rotation of the flywheel 63 is braked and consequently, the sewing machine cannot be actuated and operated.

Subsequently, when the pedal 71 is depressed for actuating the sewing machine, the arm lever 62 is rotated in the counterclockwise direction thereby overcoming the biasing force of spring 64 as a result of the downward movement of the connecting rod 70 and the clutch disc 60 is separated from the flywheel 63 and is now in contact with the flywheel 58 so as to thereby transmit the rotational drive torque from the motor 59 to the pulley 72 and hand wheel 84 whereby the sewing machine is actuated and placed into operation at a high rate of speed. Due to the rotation of arm lever 62, the switch MA is actuated so as to de-energize the brake coil 69 thereby permitting the actuation of the auxiliary motor 67 so as to rotate the flywheeel 63 through means of the worm means 65 and 66. The flywheel 63 is, however, at this stage not engaged with the clutch disc and therefore, the flywheel 63 is idly rotating at a relatively low rate of speed.

in conjunction with the actuation of switch MA, the relays R and R are actuated so as to thereby alter the positions of switches R1-1-Rl-4 and R3-l-R3-4 from the conditions illustrated within FIG. 15. The brake coil 69 is deenergized as a result of the switch Rl-l being switched over, while the auxiliary motor 67 is actuated as a result of the switches R1-2 and R1-3 being switched over so as to thereby rotate the flywheel 63 at the aforenoted low rate of speed through the worm means and 66. Under these conditions, the pedal 71 may again be released to the neutral position for the performance of a thread cutting operation, whereby the clutch disc 60 is now in contact with the flywheel 63 and thus the rotational speed of the main shaft is decreased due to the low speed rotation of flywheel 63.

At this time, the switch MA is switched over due to the releasing movement of the arm lever 62, however, the actuation of the relay R1 is now dependent upon the operation of the sensor means 85, that is, if the disc 88 of the sensor means 85 is rotated at a speed in excess of 300 R.P.M., then the relay R1 continues to be actuated so as to de-energize the brake coil 69 and to continue the actuation of the auxiliary motor 67, while if the disc 88 is rotated at a speed which is less than 300 R.P.M., then the operation of relay R1 is terminated so as to thereby in turn terminate the rotation of the main shaft at a position corresponding to the bottom dead center position of the needle. The relay R3 is, at this stage, still actuated as a result of the operation of switch R3-2.

The switch MB may be actuated by the knee of the operator for the performance of a thread cutting operation under these conditions, and subsequently, the solenoid 76 may be actuated so as to rotate or pivot the hook 74 in the clockwise directionabout the pin 75 so as to thereby engage the bent portion thereof with the hook portion 81 of the detent 78. Accordingly, even if the pedal 71 is erroneously depressed at this stage, the arm lever 62 is not able to be rotated, and consequently, during the thread cutting operation, the lever 62 will in fact not be able to be actuated. After this switch MB is actuated for energizing the solenoid 76, then the switch MC may now be moved to the ON state so as to actuate the relay R2 whereby the switch RZ-l may be changed over from the condition illustrated within FIG. 15.

This movement causes the actuation of relay R3 to be terminated, and due to the switching of switch R2-1, the brake coil 69 is also de-energized whereby the auxiliary motor 67 which is rotated thereby, is thus able to rotate the main shaft of the sewing machine at a low rate of speed. Simultaneously therewith, the first solenoid 18 is also energized due to the switching over of switch R24, and therefore, even if the sewing machine is actuated at a low rate of speed, the thread cutting operation can nevertheless be obtained. In addition, as the switch MC is actuated when the hook 74 is in contact with the planar portion 83 of the detent 78 upon energization of the solenoid 76, it is therefore apparent that even if the switch MA should be erroneously actuated when the pedal 71 is depressed so as to actuate the sewing machine at a high rate of speed during energization of solenoid 76, the thread stitching operation will not be able to be performed due to the actuation of switch MC which does not permit rotation of lever arm 62 in conjunction with solenoid 76.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is to be understood therefore that within the scope of the appended claims the present invention may be practiced otherwise than as specifically described herein.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A safety device for use in conjunction with the thread cutting mechanism of a sewing machine, comprising:

a main power source for actuating a main drive shaft of said machine for the performance of a stitching operation;

connecting means operable for connecting said main power source with said main drive shaft;

sensing means sensitive to the rotational condition of said main drive shaft and capable of generating a signal in response thereto;

a thread cutting device operable for holding and cutting the thread of said machine in response to said generated signal of said sensing means; and

detent means operatively connected to said connecting means for preventing the connection of said power source to said drive shaft during a thread cutting operation.

2. A saftey device as set forth in claim 1, wherein said thread cutting device further comprises:

a first shaft adapted to be connected to said power source;

first ratchet means disposed upon said first shaft and rotatable therewith;

first stationary blade means fixedly secured to the framework of said machine;

a second shaft disposed parallel to said first shaft;

second ratchet means disposed upon said second shaft and being axially movable relative thereto so as to selectively engage said first ratchet means;

second pivotally movable blade means connected to said second shaft; and first solenoid operated means for moving said second ratchet means along said second shaft so as to engage said first ratchet means,

whereby said second shaft will be rotated so as to in turn rotate said second blade means relative to said first blade means for the performance of said cutting operation.

3. The safety device as set forth in claim 1, wherein said detent means further comprises:

a first hooked member fixedly secured to a housing of said main power source;

a second hooked member pivotably secured to said connecting means so as to be selectively engaged with said first hooked member; and second solenoid-operated means secured to said connecting means for pivoting said second hooked member toward or away from said first hooked member,

whereupon engagement of said first and second hooked members, said connecting means is prevented frorn connecting said power source to said drive shaft.

4. The safety device as set forth in claim 1, wherein:

said connecting means is pivotably supported upon a housing of said power source and is operatively connected to a foot pedal; and

a power switch is adapted to be actuated for provid ing power to said power source upon the pivotal movement of said connecting means in response to the depression of said foot pedal.

5. The saftey device as set forth in claim 2, wherein said first solenoid means is actuated by a knee-operated switch.

6. The safety device as set forth in claim 3, wherein said second solenoid means is actuated by a kneeoperated switch.

l l i l

Claims (6)

1. A safety device for use in conjunction with the thread cutting mechanism of a sewing machine, comprising: a main power source for actuating a main drive shaft of said machine for the performance of a stitching operation; connecting means operable for connecting said main power source with said main drive shaft; sensing means sensitive to the rotational condition of said main drive shaft and capable of generating a signal in response thereto; a thread cutting device operable for holding and cutting the thread of said machine in response to said generated signal of said sensing means; and detent means operatively connected to said connecting means for preventing the connection of said power source to said drive shaft during a thread cutting operation.

2. A saftey device as set forth in claim 1, wherein said thread cutting device further comprises: a first shaft adapted to be connected to said power source; first ratchet means disposed upon said first shaft and rotatable therewith; first stationary blade means fixedly secured to the framework of said machine; a second shaft disposed parallel to said first shaft; second ratchet means disposed upon said second shaft and being axially movable relative thereto so as to selectively engage said first ratchet means; second pivotally movable blade means connected to said second shaft; and first solenoid operated means for moving said second ratchet means along said second shaft so as to engage said first ratchet means, whereby said second shaft will be rotated so as to in turn rotate said second blade means relative to said first blade means for the performance of said cutting operation.

3. The safety device as set forth in claim 1, wherein said detent means further comprises: a first hooked member fixedly secured to a housing of said main power source; a second hooked member pivotably secured to said connecting means so as to be selectively engaged with said first hooked member; and second solenoid-operated means secured to said connecting means for pivoting said second hooked member toward or away from said first hooked member, whereupon engagement of said first and second hooked members, said connecting means is prevented from connecting said power source to said drive shaft.

4. The safety device as set forth in claim 1, wherein: said connecting means is pivotably supported upon a housing of said power source and is operatively connected to a foot pedal; and a power switch is adapted to be actuated for providing power to said power source upon the pivotal movement of said connecting means in response to the depression of said foot pedal.

5. The saftey device as set forth in claim 2, wherein said first solenoid means is actuated by a knee-operated switch.

6. The safety device as set forth in claim 3, wherein said second solenoid means is actuated by a knee-operated switch.

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