US3688710A

US3688710A - Control system for a sewing machine

Info

Publication number: US3688710A
Application number: US68658A
Authority: US
Inventors: Tsutomu Makihara; Satoshige Yoneji
Original assignee: Brother Industries Ltd
Current assignee: Brother Industries Ltd
Priority date: 1970-09-01
Filing date: 1970-09-01
Publication date: 1972-09-05
Anticipated expiration: 1989-09-05

Abstract

A system comprising a sewing machine, a clutch-brake motor for driving said sewing machine at high speed, a foot treadle, and an electric circuit for controlling the machine operation. The machine is operated by the circuit in such a manner that nonravel seam is applied at the start and end of sewing at high speed when the foot treadle is operated and that no non-ravel seam is made when the machine needle is stopped in its lower position and then started from this position for the next continuous stitching.

Description

United States Patent Makihara et al.

[451 Sept. 5, 1972 [54] CONTROL SYSTEM FOR A SEWING MACHINE [72] Inventors: Tsutomu Makihan, Kariya; Satoshige Yoneji, Nagoya, both of Japan [73] Assignee: Brother Kogyo Kabushiki Kaisha,

Nagoya-shi, Japan [22] Filed: Sept. 1, 1970 [21] Appl. No.: 68,658

[52] US. Cl. ..112/219 A, 112/252 [51] Int. Cl. ..D05b 69/22 [58] Field ofSearch...ll2/2l9 A,219 R, 219B, 203,

[56] References Cited UNITED STATES PATENTS 3,363,594 1/1968 Kosrow ..112/210 Beckeretal ..ll2/2l9A Winz ..l l2/203 Primary Examiner-H. Hampton Hunter Attorney-Kemon, Palmer & Estabrook [57] ABSTRACT A system comprising a sewing machine, a clutch-brake motor for driving said sewing machine at high speed, a foot treadle, and an electric circuit for controlling the machine operation. The machine is operated by the circuit in such a manner that non-rave] seam is applied at the start and end of sewing at high speed when the foot treadle is operated and that no non-rave] seam is made when the machine needle is stopped in its lower position and then started from this position for the next continuous stitching.

4 Claims, 15 Drawing Figures PKTENTEDSEP 51912 SHEET 05 0F 13 I NVE NTOR.

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PATENTEDSEP 51912 I I 3.688.710

- vsum 130F 13 CONTROL SYSTEM FOR A SEWING MACHINE The present invention relates to a control system for a sewing machine including a non-ravel seaming device, particularly to an improvement of the control system according to applicants co-pending US. Pat. application Ser. No. 63,249 filed Aug. 12, 1970.

The conventional non-ravel seaming process at the start of sewing consists in lightly depressing a foot treadle connected to a clutch and brake motor to slow down the sewing speed of the sewing machine and under this condition continuing sewing up to a desired point, manually actuating a work feed reversing mechanism to sew the work fabric over a slight length under such condition, releasing the work feed reversing mechanism to bring the work feed back to the original direction, and, upon completions of non-rave] seaming, properly depressing the foot treadle to perform the desired normal sewing.

Also, the non ravel sewing process at the end of sewing consists in stopping the depression of the foot trea-. dle connected to the clutch and brake motor of the sewing machine as sewing is drawn near to its termination so as to slow down the sewing up to the desired point, manually operating the work feed reversing means to sew only a small portion of the work feed at reverse speed, and releasing said work feed reversing means to bring the work feed back to its normal direction and perform sewing again at normal speed.

The aforesaid conventional non-rave] seaming process has the drawbacks that there is required manual operation each time non-ravel seaming is conducted until one cycle of sewing is completed, and further, operating efficiency is reduced because sewing speed has to be slowed down.

Moreover, since the amount of non-ravel seaming is determined by the length of time during which the foot treadle is depressed and the length of time during which the work feed reversing means is operated, there will be made irregular or, in some cases, unduly insufficient non-ravel seams, which will degrade the quality of the resultant sewn products.

The present invention relates to a control system for a sewing machine which is provided with some other means than those provided in the control system according to the co-pending US. Pat. application Ser. No. 63,249 and therefore can, by means of foot treadle operation, effect automatically non-rave] seaming at the start and end of sewing of the work fabric. That is, the control system according to the present invention is free from any drawbacks that the conventional nonravel seaming process inevitably encounters, and effectively helps the sewing machine to perform desirable seaming.

The object of the present invention is to provide a control system for a sewing machine which can effect automatically, by means of foot treadle operation, nonravel seaming both at the start and end of sewing, stop the needle at its predetermined lower position by a needle positioning means after the foot treadle sewing direction with the needle as a turning axis, and prevent non-rave] seaming at any portion of the work fabric other than the start and end of sewing after seaming is initiated again at the turning point. Thus, the control system according to the non-ravel seaming, whereby the commercial value of the resultant sewn products will not be reduced.

Another object of the present invention is to provide a control system for a sewing machine to make nonravel seams in response to thread cutting operation to be carried out when .a continuous seaming is completed. Thanks to this specific means, the sewing machine in combination with the control system of the present invention makes desirable seams without making any undesirable non-rave! seams, but performs nonravel seaming, when required, at the start and end of sewing.

Still another object of this invention is to provide a control system for a sewing machine which is simple in construction and yet able to form such a desirable seaming as mentioned in the preceding paragraph.

This invention can be more fully understood from the following detailed description given by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a schematic pictorial view of an entire sewing machine according to an embodiment of the present invention which is equipped with a clutch and brake motor;

FIG. 2 schematically presents the drive mechanism of said sewing machine;

FIG. 3 is an elevation, partly broken away, of a clutch and brake motor; 2

FIG. 4 is a bottom view of the operating mechanism of the clutch and brake motor of FIG. 3;

FIG. 5 is a cross sectional view of FIG. 3;

FIG. 6 is a cross sectional view of an auxiliary motor attached to the clutch and brake motor of FIG. 5;

FIG. 7 is a cross section of the treadle of the sewing machine of FIG. 1;

FIG. 8 is a cross sectional view of the ring switch mechanism of the sewing machine of FIG. 1;

FIG. 9 is a cross sectional view of the individual ring switches where the switch mechanism of FIG. 8 is dismembered;

FIG. 10 illustrates the relative positions of the ON" and OFF of the respective ring switches;

FIG. 11 is a schematic pictorial view of the work feed mechanism of the sewing machine of FIG. 1;

FIG. 12 indicates an electrical control circuit for driving the sewing machine of FIG. 1;

FIG. 13 is a time chart for explanatory illustration of the sewing machine operation; and

FIG. 14A and 14B show a modification of actuating lever structure of the sewing machine.

Referring to FIGS. 1 and 2, the reference numeral 20 denotes a sewing machine, and 21 is its main shaft rotatably supported on the frame of said sewing machine 20. Said main shaft, is fitted with a pulley 22 and ring switch assembly 23 as will be later set forth. 24 is a reciprocable needle supported on the frame and drivingly connected to the

main shaft

21, and 25 is a presser foot urged downward by a built-in spring 26. Said foot member 25 is coupled with an interlocking mechanism 30 consisting of a lever 27, connection rod 28, and bell crank 29. The interlocking mechanism 30 is connected to the piston rod 32 of a first fluid pressure cylinder 31. 33 is an electrical control valve attached to the first fluid pressure cylinder 31 so as to transfer fluid stream. Said electrical control valve 33 is actuated upon energization by a first solenoid 34 to lift the presser foot 25 and keep it at an upper position. 40 is a thread cutting mechanism rockably fitted to the underside of a throat plate, which is connected to the piston rod 36 of a second fluid pressure cylinder 35. 37 is an electrical control valve attached to the second fluid pressure cylinder so as to transfer fluid streams. On both sides of said valve 37 are disposed second and

third solenoids

38 and 39 which are alternately energized. Movement of the piston rod 36 upon energization by the second solenoid 38 causes the tread cutting mechanism 40 to rock one way to take hold of upper and lower threads, while movement of the piston rod 39 causes the thread cutting mechanism 40 to rock the other way so as to cut thread.

A clutch and brake motor as shown in FIGS. 2 to 6 includes a main motor 41 disposed in a bracket 42, which consists of a stator 43 and rotor 44. One end of the rotary shaft 45,- FIG. 3, of the rotor 44 extends through a bearing 46. To the projecting end of said rotary shaft 45 is fixed by a bolt 48 a flywheel 47 fitted with a friction plate 56. 49 is a hollow bearing cylinder received in an end bracket 50 in coaxial relationship with the rotary shaft 45.

With the periphery of the bearing cylinder 49 is rotatably engaged an annular worm wheel through a bearing 51. 52 is a brake wheel having a friction plate 53 fitted on one side. This brake wheel 52 is connected by bolt 54 to that side of the work wheel 55 which faces the flywheel 47. 58 is a movable shaft supported to a sleeve 57 joumaled in the bearing cylinder 49 so as to slide therethrough in its axial direction. To the inner end of said shaft 58 is connected by a bolt 61 a clutch disk interposed between the friction plates 53 and 56. To the outer end of said shaft 58 is connected a pulley 62 by a bolt 63. is an auxiliary motor, FIG. 6, which consists of a stator 71 and rotor 72. One end of theshaft 77 of the rotor 72 is supported on one end bracket 73 through a bearing 74 and the other end of said shaft 77 projects through a bearing 76 from the other end bracket 75. Outside of the end bracket are provided inner and outer chambers 78 and 79 partitioned by a double cylindrical wall disposed around the rotary shaft 77. To that end of the rotary shaft 77 which projects into the inner chamber 78 is fixed by a bolt 82 a connection wheel 81 having a friction engaging member fitted to its side. In the outer chamber 79 is received a clutch coil 83, for example, an annular solenoid. 84 is a clutch side bracket connected to the end bracket 75 and 85 is a worm gear side bracket connected to said clutch side bracket 84 by a bolt 86. The latter bracket 85 is integrally formed with the end bracket 50 facing the main motor 41. 87 is a worm gear engaging the worm wheel 55. One end of a shaft 88 integrally formed with said worm gear 87 is pivoted to the outer end of the bracket 85. The other end of said shaft 88 is inserted into the clutch side bracket 84 with the intermediate portion supported by a bearing 89. 90 is a coil case received in the clutch side bracket 84 so as to surround the shaft 88. This coil case 90 houses a brake coil 141, and an attractive plate 91 constitutes a slide contact member 93, and is connected by a bolt 92 to the clutch side bracket 84. 94 is a clutch disk fitted with a brake member 95 slidable on the shaft 88 in the axial direction thereof. Said clutch disk 94 is interposed between the friction engaging member 80 of the connection wheel 81 and the contact member 93 and is connected to the end of the shaft 88 so as to move in its axial direction. is a main actuating lever assuming as a whole an L-shape, FIG. 3. The two portions divided by the bent point are designated as one arm 101 and the other arm 102 respectively. From the bend of said main actuating lever 100 projects a two-forked pressure contact means 103a comprising a pressure contact member 103. The end of said one arm 101 is rotatably supported by a shaft pin 105 on a support member 104 projecting from the end bracket 50. 106 is a spring support rod freely penetrating said one arm 101, one end of said rod 106 being fixed to the end bracket 50. Into the end bore of said one arm 101 penetrated by the spring support rod 107 is idly inserted a coil spring so as to press said one arm 101. Said spring107 is kept in a compressed state by screwing a wing nut 108 into the end of the spring support rod.

106. 109 is a stopper screwed throughout said one arm 101. The end of said stopper 109 normally contacts the end bracket 50 and is prevented from being loosened by a nut 110. 111 is an intermediate lever whose cross section substantially assumes a horizontally thrown U- shape. Said lever 111 is rotatably connected at a certain point along the length to the end of said other arm 102 by a shaft pin 112. Substantially to the indicated right side end of said lever 111 is fitted by a screw 114 a thread cutting switch 8;, comprising an actuating strip 113. 115 is a coil spring, part of which is received in a recess 116 formed in said other arm 102. The upper end of said coil spring 1 15 contacts the underside of the end of the intermediate lever 111. Said coil spring 1 15 is guided by a bolt 117 idly penetrating the end of the intermediate lever 111, said bolt 117 being embedded in said other arm 102. 118 is a stopper penetrating throughout the intermediate lever 111. The lower end of the stopper 118 contacts the end of said other am 102. 119 is an actuating plate which is fixed by a screw 120 to the end of said other arm 102 in such a manner as to face the actuating strip 113 of the thread cutting switch 5;. Into that part of said actuating plate 119 which faces the actuating strip 113 is inserted a press screw 121. 122 is an auxiliary actuating lever consisting of a pair of plate members surrounding said one arm 101 of the main actuating lever 100, the intermediate part of said lever 122 being rotatably pivoted to the shaft pin 105. The upper end of said lever 122 is connected through an opening 123 formed in the underside of the bearing cylinder 49 to a shaft pin 124 engaging the annular groove 59 of the sleeve 57. To the lower end of the auxiliary actuating lever 122 is horizontally fitted another shaft pin 125, FIG. 4. The shaft pin 125 is contacted by the press member 103 of the main actuating lever 100. 126 is a connection member rotatably connected to the shaft pin 125 and there is interposed a coil spring 128 in a compressed state between one end of said connection member 126 and a spring support 127 substantially assuming a horizontally thrown U- shape which is fixedto the main actuating lever 100.

- 129 is a fluid pressure cylinder including a fourth solenoid 129a. When there is introduced high pressure fluid into the cylinder 129, upon energization of the solenoid 129a, the piston rod 130 of which is pushed forward. The fluid pressure cylinder 129 is fitted through a support plate 131 below said other arm 102 of the main actuating lever 100 by a shaft screw 132 in a manner to rotate about it. The end of the piston rod 130 is integrally connected to the other end of the connection member 126. 134 as shown in FIG. 1 is a foot treadle positioned below a sewing machine bed 135. The treadle 134 is fitted with a connection rod 136, the upper end of which is connected to the end of the intermediate lever 111. Said foot treadle is normally positioned at a rest position and operable in a downward direction to actuate the main actuating lever 100 and an upward direction beyond the rest position. Into the lower end of the auxiliary actuating lever 122 is inserted a press screw 142, FIG. 4 in a manner to penetrate it. The screw 142 is prevented from being loosened by a nut 143. S denotes a start switch fitted to a support 135 mounted on the bracket 50. The start switch S is normally opened with its actuating strip 146 pressed by the press screw 142, and closed when the actuating strip 146 is released.

There will now be described the operation of a clutch and brake motor constructed as above described. Let it be assumed that the main motor 41 and the auxiliary motor 70 are brought into an operable state without any manual operation applied to the main and

auxiliary levers

100 and 122. Since the brake member 52 and clutch disk 60 are separated, the flywheel 47 continues no-load rotation. On the other hand, where, on the side of the auxiliary motor 70, the clutch coil 83 is excited, the clutch disk 94 frictionally engages the friction engaging member 80 of the connection wheel 81 to cause the worm gear 87 to rotate, and in consequence the worm wheel 55 engaging the worm gear 87 slowly rotates around the bearing cylinder 49. Under such condition, namely, where the foot treadle 134 is not depressed but keeps a neutral position, the clutch disk 60 on the side of the main motor 41 is pressed, as described later, to the friction plate 53 of the worm wheel 55 by the action of the coil springs 107 and 128. Accordingly, the rotation of the worm wheel 55 is transmitted to the pulley 62 through the clutch panel 60 and movable shaft 58. At this time, the pulley 62 is in a slowly rotating state. When, under such condition, the foot treadle 134 is depressed in the downward 134 is released, the clutch disk 60 is pressed to the side 7 of the worm wheel 55. Where the brake coil 140 is direction that is, toward the start side), then the intermediate lever 11 1 is pulled downward through the connection rod 136, and the other arm 102 of the main actuating lever 100 is depressed by the joint action of the stopper 118 and shaft pin 112 of said intermediate lever 111 to rotate about the shaft pin 105 in the direction indicated by the arrow 137. As a result, the press contact member 103 presses the shaft pin 125, causing the auciliary actuating lever 122 to rotate about the shaft pin 105 similarly in the direction indicated by the arrow 137. Accordingly, the sleeve 57 moves through the shaft pin 124 in the direction indicated by the arrow 138, carrying with it the movable shaft 58, so that the clutch disk 60 is pressed to the friction plate 56 of the flywheel 47 which is rotating without load and is frictionally coupled with said wheel 47, with the resultant high speed rotation of the pulley 62. In the aforesaid operation, the coil spring 107 supplies the main actuating lever 100 with a force to rotate opposite to the direction indicated by the arrow 137. The other coil spring 128 supplies the auxiliary actuating lever 122 with a force to rotate similarly opposite to the direction of the arrow 137. When the foot treadle excited while the pulley 62 slowly rotates, the clutch disk 94 is attracted thereby and the brake member 95 of said disk 94 slides to the slide contact member 93 so as to effect braking, with the resultant stop of the pulley 62. The clutch and brake motor can be controlled only by means of the fluid pressure actuating means 129. Where the electrical control valve of the fluid pressure cylinder 129 is energized to conduct high pressure fluid into the cylinder to cause the piston rod 130 of said cylinder 129 to be pushed forward to rotate the auxiliary actuating lever 122 in the direction of arrow 137 when the foot treadle 134 is operated in the upward direction beyond the rest position. When the electrical control valve is deenergized, the high pressure fluid ceases to be supplied, causing the auxiliary actuating lever 122 to be returned by the action of the coil springs 107 and 128. The coil spring 1 15 serves to energize the intermediate lever 111 for its rotation about the shaft pin 112 in the direction of the arrow 147 and also normally to leave the thread cutting switch S open by causing the press strip 113 to contact the press screw 121.

There will now be described a modification of the actuating lever structure with reference to FIGS. 14A and 14B.

FIG. 14A shows normally operating conditions while FIG. 14B shows a non-ravel seaming operation.

The apparatus includes a main actuating lever 338 associated with the foot treadle, which is' swingable around an axle 339. The cutting portion 340 formed at one end of the lever 338 is abruptly stopped by a fixed axle 342 projected from a displacement body 341 through which the axle is loosely inserted. Numeral 343 denotes an auxiliary actuating lever pivoted on the axle 339, one end of the lever 343 being connected to the fixed axle and the other end to a piston rod 345 of pressure cylinder 344 mounted on the actuating lever 338. 346 shows an actuator of the cylinder 344 where there are provided two

solenoids

348 and 349 alternatively operating. Numeral 347 denotes a coil spring provided between both

levers

338 and 343 in such a manner that it urges both levers to swing them in the opposite directions. Reference P is a pressure source. In the apparatus there is a switch, though not shown in the figures, which starts the machine operation when the foot treadle is operated in the upward direction beyond the rest position.

The treadle 134 is provided, as shown in FIG. 7, with a normally closed switch S for lifting the pressure foot which is turned off prior to the operation of the switch S in the initial stage of the depression of the foot treadle 134 in the downward direction and a thread cutting switch S for closing the thread cutting control circuit which is turned on by the operation of the foot treadle 134 in the upward direction beyond the rest position. The switch S is disposed on the underside of an auxiliary treadle 134a consisting of, for example, a flexible plate which is located at the rear part of the foot treadle 134. Where the foot treadle is not depressed either way, that is, is left in an inoperable state, the main actuating lever causes the clutch disk 60 to contact the brake wheel 52.

There will now be described the ring switch assembly 23 mounted on the main shaft 21 of the sewing machine which acts as a mechanism for arresting the needle at a prescribed position, with reference to FIGS. 8 to 10 where the needle is brought down. The ring switch assembly 23 consists of a common ring 150 fixed on the main shaft 21, a thread cutting position detecting ring 151 wherein a periphery extending through about 300 is designated as an OFF region, a needle upper position detecting ring 152 wherein a periphery of about 60 is defined as an OFF region, and a needle lower position detecting ring 153 whose OFF region is represented by a periphery of about 17. The phases of the ON and OFF and regions of the

other rings

151, 152 and 153 are so adjusted as to have a relation shown in FIG. 10. The

rings

151, 152 and 153 are contacted by

brushes

151a, 152a and 153a to constitute a thread cutting position detecting contact 8,, needle upper position detecting contact S, and needle lower position detecting contact S, respectively.

Referring to the work feed mechanism shown in FIG. 1 1, the reference numeral 160 denotes a two-forked rod engaged at one end with the work feed cam 161 of the main shaft 21 and at the other end with a horizontal work feed advancing shaft 162. This shaft 162 rocks by the rotation of the work feed cam 161. 163 is a work feed bar provided with a feed dog 164. Said work feed bar 163 is connected at one end to the horizontal work feed advancing shaft 162 so as to rock horizontally, and at the other end to a pendulum 166 mounted on a vertical feed lifting shaft 165 in a manner to rock vertically. When the horizontal feed advancing shaft 162 and vertical feed lifting shaft 165 rock, the feed dog 164 makes four feed motions by a composition of said rockings to perform a work feed action. A feed reversing means involved in the work feed mechanism is operated in the following manner. 167 is a feed adjusting means disposed at the fulcrum of the two-forked rod 160 and provided with a dial 167a for controlling the work feed. To said feed adjusting means 167 is connected the feed reverse arm 170 of a reversing shaft 169 provided with a reversing lever 168. When this reversing lever 168 is pushed down, the feeding direction of said dog 164 is turned from a forward to a backward movement on the bed of a sewing machine. 171 is a fourth fluid pressure cylinder rockably supported by a pin 173 on a support member 172 fitted to the underside of said machine bed. The piston rod 174 of the cylinder 171 is connected to an arm 175 fixed to the reversing shaft 169. To the arm 175 is connected a spring member 176 for urging the reversing shaft 169 in an oppositedirection. 177 is an electrical control valve for transferring fluid streams which is attached tothe fourth fluid pressure cylinder 171. The electrical control valve 177 is provided with a fifth solenoid 178, which, when energized, feeds fluid streams in a direction of pushing up the piston rod 174. Energization of the solenoid 178 causes the piston rod 174 to be forced upward, the reversing shaft 169 to rotate in an opposite direction and the feed dog 164 to move backward. 179 is a source of compressed fluid, for example, a compressor.

There will now be described with reference to FIG. 12 an electrical control circuit to effect the proper function of the entire sewing machine mechanism. The reference numeral 181 is a transformer, whose primary winding 182 is connected to an AC. source 183. Both ends of the secondary winding 184 of the transformer 181 are connected to two buses or power source lines 186 and 187 through one full wave rectifier 185. Across the power source lines 186 and 187 is a smoothing circuit consisting of a resistor 188 and condenser 189 connected in series. The circuit energized by the voltage impressed across the power source lines is arranged as follows. Across the power source lines is connected a serial circuit consisting of the start switch S diode 191 and relay 190 energized through the diode 191 by the closure of the switch 8,. Across the cathode of the diode 191 and the first power source line 186 is connected a serial circuit comprising the normally open contact element 190a of the relay 190 and a needle lower position detecting contact element 5,. Thus these serial circuits constitute the self-holding circuit of the relay 190. Parallel with the needle lower position detecting element S, is connected a serial circuit consisting of a condenser 192 and diode 193 for preventing inverse discharge, to which there is connected a resistor 194. 195b, is the normally closed contact element of the later described thread cutting relay 195, one end of which is connected to the first line 186 and the other end of which is connected to a control line 197 through the normally open side of the switching contact element 1960 of the later described relay 196. Across the control line 197 and the anode of the diode 191 are connected a three-terminal thyristor 198 and start non-ravel seaming switch 8,. Accordingly, the control line 197 is supplied with power by the first power source line through the start switch S,, and elements 8; and 198. Between the control line 197 and second line 187 are connected a serial circuit consisting of the relay 196 and three-terminal thyristor 199 and a simulation load 200. 201 is another control line connected to said control line 197 through the normally closed side of the switching contact element 1960,. Between the control line 201 and second line 187 is disposed a timer device 202 energized by the voltage prevailing therebetween so as to set the time of reversion.

The timer device 202 is intended to actuate the work feed reversion mechanism in a prescribed length of time after the start of a sewing machine. Said timer device 202 is arranged as follows. Between the control line 201 and second line 187 is connected a serial circuit consisting of a resistor 203 and constant voltage diode 204. Parallel with said diode 204 is connected a time constant circuit consisting of a resistor 205, variable resistor 206 and condenser 207 connected in series. Further parallel with the diode 204 is connected a unijunction transistor 209, through

resistors

210 and 21 1 connected to the base regions of the transistor. The emitter of the transistor 209 is connected to the juncture between the variable resistor 206 and condenser 207. Accordingly, the transistor 209 is energized by a voltage prevailing across both terminals of the constant voltage diode 204. Between the control line 201 and second line 187 are connected in series a relay 213 and three-terminal thyristor 212. The gate of the thyristor 212 is connected through a diode 214 to the juncture between the transistor 209 and resistor 211. Thus the diode 214 is energized by a voltage prevailing across the terminal of the resistor 21 1.

With the timer device 202 of the aforementioned arrangement, when the control line 201 is impressed with a voltage, the condenser 207 begins to be charged. When the terminal voltage of the condenser 207 attains a prescribed value after a preset time (as determined by the resistivities of the

resistors

203, 205 and 206 constituting a time constant circuit), then the transistor 209 is conducted and the thyristor 212 is also conducted by being supplied with gate signals through the diode 214 to actuate the relay 213.

The reference numeral 215indicated in the circuit denotes a reversion timer device concurrently acting as the first and second timer devices which set the period during which the work feed and reversion mechanisms are separated when non-rave] seaming is performed at the start and end of sewing.

To this reversion timer device, there is connected between the buses 186 and 187 a serial circuit consisting of the fifth solenoid 178 and transistor 226. Between the control line 201 and second line 187 are connected the normally open contact element 213a of the relay 213, a diode 217 and a resistor 252. To the cathode of the diode 217 is connected further control line 216, to which there is connected one end of still further control line 218 through a resistor 219. To the other end of the control line 218 are connected in turn a resistor 220, two variable resistors 221 and 222 alternately actuated by the switching contact element 213C of the relay 213 and a condenser 223 connected to said resistors 221 and 222, thus constituting a time constant circuit. The reference numeral 224 is a unijunction transistor, one base of which is connected to the control line 218 through a resistor 225, the other base of which is connected to the second line 187 through the primary winding PT of a first pulse transformer PT,, and the emitter of which is connected to the juncture between the resistors 22] and 222 and the condenser 223. As the result, the emitter is energized by a voltage impressed across the condenser 223, thereby causing the transistor 224 to be conducted in a prescribed length of time. Between the cathode of the diode 217 and second line 187 is connected a serial circuit consisting of a resistor 228 and three-terminal thyristor 227. The anode of the thyristor 227 is connected to the base of the transistor 226. The reference numeral 231 shown in the figure denotes a constant voltage diode interposed between the control line 218 and second line 187. 253 and S respectively represent a diode connected between the

line

186 and 187 and a manual switch for manually operating the work feed and reversion mechanisms. Further between the power source lines 186 and 187 is connected a serial circuit consisting of an upper position detecting switch S normally open thread cutting switch the normally closed contact element 229b and relay 230 associated with the switching contact element 1906 of the relay 190. The reference numeral 232 denotes further control line, which is connected through the terminal nonravel seaming switch S to the juncture between the thread cutting switch S and switching contact element 190e,. To the thread cutting switch S is connected is parallel the normally open contact element 233a of the relay 233. Between the control line 232 and second line 187 are respectively connected a relay 229 energized by a voltage impressed therebetween two bases of a transistor 234 are directly connected to said relay 229 and the base 187. To the control line 232 is connected further control line 237 through a three-terminal thyristor 235 and resistor 236. Between the control line 237 and second line 187 is provided a timer device 238 of substantially the same arrangement as the aforementioned timer device 202, which also sets the point of time at which sewing is brought to an end. Referring to said timer device 238, the reference numerals 239 to 242 indicate resistors, 243a condenser 240a a variable resistor, 244 a unijunction transistor, 245 a diode, and 246 a three-terminal thyristor serially connected to the resistor 242. The anode of the thyristor 246 is connected through a resistor 247 to the base of the transistor 234.

The movable strip of the switching contact element 2330 of the relay 233 is connected to the first line 186, and the fixed contact strip on the normally open side of the switching contact element 233c is connected to the normally open side of the switching contact element 1900,. The brake coil 140 which is connected at one end to the first line 186 is connected at the other end to v the second line 187 through the normally closed side of the switching contact element 1900 of the relay and also through the normally closed side of the switching contact element 2300 of the relay 230. The clutch coil 83 (FIG. 6) which is connected at one end to the first line.l86 is connected at the other end to the second line 187 through the normally open side of the switching contact element 230e,. The fixed contact element on the normally open side of the switching contact element 2330, is connected to the fixed contact element on the normally open side of the switching contact element 190e To the normally closed side of the switching contact element 2330 are connected the first solenoid 34 and manual switch S for downwardly moving the presser foot 25 in turn. The normally closed switch for lifting the pressurefoot is connected to the fixed contact element on the normally closed side of the switching contact element 1900 The reference numeral 229a, is the normally open contact element of the relay 229. Between the first and

second lines

186 and 187 is connected a serial circuit consisting of said normally open contact element 229a, and the fourth solenoid 129a serially connected thereto. Further between the power source lines 186 and 187 are connected a serial circuit consisting of the thread cutting portion detecting contact element 8,, thread cutting relay and the normally open contact element 230a of the relay 230 and another serial circuit consisting of the second solenoid 38, and the normally open side of the switching contact element 195a of the relay 195. The normally closed side of the contact element 195a is connected to the power source line 186 through the third solenoid 39 The reference numeral 248 shown in the figure is a three-terminal thyristor, the anode of which is connected to the first line 186 through the normally open contact element 229a of the relay 229 and the cathode of which is connected to the control line 216. The reference character PT denotes the primary winding of a second pulse transformer PT Said winding BT is connected at one end of the second line 187 and at the other end is connected to a parallel circuit consisting of a resistor 249 and condenser 250 and to the first line through the thread cutting position detection element 8,. The two secondary windings designated as PT of the first pulse transformer PT, are connected between the cathodes and gates of the two

thyristors

199 and 227. The three secondary windings indicated as PT of the second pulse transformer PT, are respectively connected between the cathodes and gates of the three

thyristors

198, 235 and 248. 251 denotes the gate bias resistors of the

thyristors

198, 199, 212, 235, 246, 227 and 248; 252 is a resistor for assuring power supply to conduct each of the

thyristors

235 and 248; and 253 is a diode for controlling spike voltage.

There will now be described with reference to the time chart of FIG. 13 the non-ravel seaming operation of a sewing machine constructed as described above. The lines of the figure present the operating condition.

I. Start (Refer to FIG. 13)

When there is thrown the power source switch of the main and auxiliary motors (not shown), the motor 41 is brought into an operable state and there is supplied an alternating current from the AC. source 183 through the transformer 181 to the full wave rectifier 185, where the alternating current is subjected to full wave rectification, so that there is impressed a DC. voltage across the power source lines 186 and 187. When the aforesaid power source switch is closed, there are also manually thrown the start and end non-ravel seaming switches S, and S Under such condition, the first solenoid 34 is energized through the switch S and the normally closed side of the three switching contact elements 233c,, 190c, and 2300,. The piston rod 32 of the first fluid pressure cylinder 31 is urged in a direction of pushing the connection rod 28 to lift the pressure foot 25 against the built-in spring 26. On the other hand, the fourth solenoid 129a for the auxiliary actuating lever 100 is not actuated, so that said control lever 122 is kept parallel with part 101 of the main actuating lever 100 through spring 108.

II. Sewing and start non-rave] seaming operation (Refer to T, to T, in FIG. 13)

When the foot treadle 134 is depressed in the downward direction from the rest position to drive a sewing machine, the switch S is opened by the auxiliary treadle 1340 to deenergize the first solenoid 34, so that the presser foot 25 is brought down by the spring 26 to keep the work on the machine bed. At the time of T, of FIG. 13 the start switch S, is closed and the main actuating lever 100 rotates about the shaft 105 in the direction of the arrow 137, causing the auxiliary actuating lever 122 to move the sleeve 57 with the movable shaft 58, and the clutch disc 60 to be pressed to the fly wheel 56 in high speed rotation. Thus the main shaft 21 is turned quickly to start the sewing operation. When the sewing machine makes such a high speed run, the ring switch assembly 23 is also brought into an operable state. The thread cutting position detecting contact element 8,, needle upper position detecting contact element S, and needle lower position detecting contact element S involved in the ring switch assembly 23 are operated with a period shown in FIG 13. In the meantime the primary winding PT,, of the second pulse transformer PT, is energized by pulses from the thread cutting portion detecting contact element S, to generate pulses synchronizing therewith in the secondary winding of the transformer PT,. On the other hand, the closure of the start switch S, causes the relay to be actuated and brought into a self-holding position by the current flowing through the normally open contact element 190a, and needle lower portion detecting contact element 8,. In this case, the needle lower position detecting contact element S, is turned off each time the brush 153a passes through the OFF region of the needle lower position detecting ring 153. Since, however, the main shaft 21 of the sewing machine is rotated at high speed, the relay 190 is kept in a self-holding position by the current discharged from the condenser 192 during the OFF period of the needle lower position detecting contact element 5,. At this time the switching contact elements 190a, and 190e, of the relay 190 are charged over, causing the clutch coil 83 to be excited by the latter contact element 1900,. Since the clutch disk 94 is attracted to said connection wheel 80, the clutch disk 60 is driven through the worm 87 and worm gear 55 into a slow noload operation. When the sewing operation is reliably started, namely, when the thread cutting portion detecting contact element S, starts operation to cause pulses to be generated in the secondary winding PT of the second pulse transformer PT then the thyristor 198 is conducted to supply voltage to the

control lines

197 and 201 and energize the timer device 202. After a prescribed length of time (at the time T, in FIG. 13), the transistor 209. is conducted by the charged current of the condenser 207, with the resultant conduction of the thyristor'212, so as to actuate the relay 213. Accordingly, the variable resistor 222 is selectively operated by the switching contact element 213c, and the reversion timer device 2l5-is energized by the closure of the normally open contact element 213a,. As the result, the transistor 226 is conducted by the current passing through the resistor 228 to excite the fifth solenoid 178. The piston rod 174 of the fourth fluid pressure cylinder 171 is pushed upward and in consequence the feed dog 164 is changed to make a backward movement opposite to that which it has performed up to this point, so as to reverse the work feed and start non-ravel seaming quickly. This non-rave] seaming is continued until the period preset by the reversion timer device 215 is brought to an end. When the lapse of said period is determined by the time constant defined by the variable resistor 222 and condenser 223, the transistor 224 is conducted to energize the primary winding PT,, of the first pulse transformer PT, and generate pulses in the secondary winding PT, thereof (at the time T, in FIG. 13). As the result, the thyristor 227 is conducted and the transistor 226 is shut off to deenergize the fifth solenoid 178, so that the reversing shaft 169 is made to rotate in the normal direction by the spring 176 and the feed dog 164 again starts a forward movement. Upon deenergization of the fifth solenoid 178, the pulses generated in the secondary winding PT of the first pulse transformer PT,, conduct the thyristor 199 to actuate relay 196 and change over the switching contact element 1960,. As the result, the relay 196 is kept in a self-holding position, and power supply to the control line 201 is stopped. The relay 213 is brought back to its original position to open its normally open contact element 213a, which has been closed up to this point, bringing the control line 216 into an unconducted state, thus preventing the

Claims

1. A control system for a sewing machine having a frame, a main shaft rotatably mounted on said frame, a reciprocable needle supported on said frame and drivingly connected to said main shaft, a work feeding means supported on said frame for advancing or reversing the travel of a work fabric according to the rotation of said main shaft, and a feed reversing means supported on said frame for reversing the feeding direction of said work feeding means; the control system comprising: 1. drive means drivingly connected to said main shaft for rotating the same, 2. clutch means provided between said drive means and said main shaft for operatively connecting said drive means with said main shaft, 3. a foot treadle operable from a rest position in a downward direction and in an upward direction beyond the rest position, said foot treadle operably connected to said clutch means and operable in said downward direction for actuating the clutch means to rotate said main shaft, 4. auxiliary actuating means operably connected to said clutch means for actuating the same in replacement of said foot treadle, 5. operating means connected to said auxiliary actuating means for operating the same, 6. needle positioning means provided between said drive means and said main shaft for stopping saId needle in a predetermined upper or lower position, said needle positioning means being adapted to stop said needle in the lower position upon return of said foot treadle to its rest position from the downward direction and to stop said needle in the upper position upon operation of said foot treadle to its upward direction beyond the rest position, 7. first control means connected to said feed reversing means for actuating the same for a predetermined period upon operation of said foot treadle in the downward direction, 8. second control means connected to said first control means for interrupting the operation of said first control means in spite of the operation of said foot treadle in the downward direction when said needle is started from the lower position for the next continuous stitching, 9. third control means connected to said operating means and said feed reversing means for actuating both of said means for a predetermined period upon the operation of said foot treadle in the upward direction before the operation of said needle positioning means after the desired amount of sewing is finished, 10. fourth control means connected to said second control means for establishing said first control means in an operable condition when said foot treadle is operated in the upward position.

2. clutch means provided between said drive means and said main shaft for operatively connecting said drive means with said main shaft,

2. A control system for a sewing machine having a frame, a main shaft rotatably mounted on said frame, a reciprocable needle supported on said frame and drivingly connected to said main shaft, work feeding means supported on said frame for advancing or reversing the travel of a work fabric according to the rotation of said main shaft, feed reversing means supported on said frame for reversing the feeding direction of said work feeding means, thread cutting means supported on said frame, means supported on said frame for moving the thread cutting means; the control system comprising:

3. a foot treadle operable from a rest position in a downward direction and in an upward direction beyond the rest position, said foot treadle operably connected to said clutch means and operable in said downward direction for actuating the clutch means to rotate said main shaft,

3. A control system for a sewing machine having a frame, a main shaft rotatably mounted on said frame, a reciprocable needle supported on said frame and drivingly connected to said main shaft, work feeding means supported on said frame for advancing or reversing the travel of a work fabric according to the rotation of said main shaft, feed reversing means supported on said frame for reversing the feeding direction of said work feeding means, thread cutting means supported on said frame, and means supported on said frame for moving said thread cutting means; the control system comprising:

4. auxiliary actuating means operably connected to said clutch means for actuating the same in replacement of said foot treadle,

4. A control system according to claim 3, wherein said fourth circuit is so designed as to interrupt the operation of said first and second circuits responsive to the completion of the operation of said second circuit.

5. operating means connected to said auxiliary actuating means for operating the same,

6. needle positioning means provided between said drive means and said main shaft for stopping saId needle in a predetermined upper or lower position, said needle positioning means being adapted to stop said needle in the lower position upon return of said foot treadle to its rest position from the downward direction and to stop said needle in the upper position upon operation of said foot treadle to its upward direction beyond the rest position,

6. needle positioning means provided between said drive means and said main shaft for stopping said needle in a predetermined upper or lower position, said needle positioning means being adapted to stop said needle in the lower position upon return of said foot treadle to its rest position from the downward direction and to stop said needle in the upper position upon operation of said foot treadle in its upward direction beyond the rest position.

6. needle positioning means provided between said drive means and said main shaft for stopping said needle in a predetermined upper or lower position,

7. a circuit network interconnecting said feed reversing means, said moving means for thread cutting means, said operating means, said needle positioning means, for operating the same in response to the operation of said foot treadle including; a. a first circuit for actuating said feed reversing means after predetermined period of time responsive to the operation of said foot treadle in the downward direction, b. a second circuit for actuating said feed reversing means for a predetermined period of time responsive to the completion of the predetermined time of said first circuit, c. a third circuit for operating said needle positioning means to stop said needle in the lower position upon return of said foot treadle to its rest position from the downward direction, d. a fourth circuit for interrupting the operation of said first and second circuits in spite of the operation of said foot treadle in the downward direction when said needle is started from the lower position for next continuous stitching, e. a fifth circuit for actuating said feed reversing means for a predetermined period of time responsive to the operation of said foot treadle in the upward direction after the amount of sewing is finished, f. a sixth circuit for actuating said operating means for a predetermined period of time substantially equal to or longer than that of said feed reversing means responsive to the operation of said foot treadle in the upward direction. g. a seventh circuit for operating said needle positioning means to stop said needle in the upper position responsive to the completion of the operation of said fifth and sixth circuits, h. an eighth circuit for operaTing said moving means to cut the thread after said needle was raised in the upper position by said needle positioning means, i. a ninth circuit for establishing said first and second circuits in an operable condition responsive to the energization of said eight circuit.

7. a first control means operatively connected to said feed reversing means for actuating the same after a predetermined period responsive to the operation of said foot treadle in the downward direction,

7. first control means connected to said feed reversing means for actuating the same for a predetermined period upon operation of said foot treadle in the downward direction,

8. second control means connected to said first control means for interrupting the operation of said first control means in spite of the operation of said foot treadle in the downward direction when said needle is started from the lower position for the next continuous stitching,

8. a second control means operatively connected to said feed reversing means for actuating the same for a predetermined period responsive to the completion of the predetermined period of the first control means,

9. a third control means connected to said first and second control means for interrupting the operation of said first and second control means in spite of the operation of said foot treadle in the downward direction when said needle is started from the lower position for next continuous stitching,

9. third control means connected to said operating means and said feed reversing means for actuating both of said means for a predetermined period upon the operation of said foot treadle in the upward direction before the operation of said needle positioning means after the desired amount of sewing is finished,

10. fourth control means connected to said second control means for establishing said first control means in an operable condition when said foot treadle is operated in the upward position.

10. a fourth control means connected to said feed reversing means for actuating the same for a predetermined period responsive to the operation of said foot treadle in the upward direction after the desired amount of sewing is finished,

11. a fifth control means connected to the operating means for actuating the same for a period substantially equal to or longer than that of said feed reversing means responsive to the operation of said foot treadle in the upward direction,

12. a sixth control means for actuating said needle positioning means and said moving means for said thread cutting means responsive to the termination of the operation of said operating means and said feed reversing means,

13. a seventh control means connected to said first and second control means forestablishing said first and the second control means in an operable condition responsive to the operation of said thread cutting means.