US3157261A

US3157261A - Programmed start and stop for a machine such as a sewing machine

Info

Publication number: US3157261A
Application number: US136564A
Authority: US
Inventors: Bono Luigi
Original assignee: Necchi SpA
Current assignee: Necchi SpA
Priority date: 1961-02-10
Filing date: 1961-09-07
Publication date: 1964-11-17
Anticipated expiration: 1981-11-17

Description

Nov. 17, 1964 L. BONO PROGRAMMED START AND STOP FOR A MACHINE SUCH AS A SEWING MACHINE Filed Sept. 7, 1961 3 Sheets-Sheet 1 INVENTOR LUIGI BONO ATTORN EYS Nov. 17, 1964 L. BoNo PROGRAMMED START AND STOP FOR A MACHINE SUCH AS A SEWING MACHINE Filed Sept. 7, 1961 3 Sheets-Sheet 2 INVENTOR LUIGI BONO ATTORNEYS Nov. 17, 1964 BONO PROGRAMMED START AND STOP FOR A MACHINE sucH AS A SEWING MACHINE 3 Sheets-Sheet 3 Filed Sept. 7, 1961 I INVENTOR Luigi 5on0 ATTORNEYS United States Patent 3,157,261 PROGRAMMED START AND STOP FOR A MA- CHINE SUCH AS A SEWING MACHINE Luigi Bono, Pavia, Italy, assignor to Necchi Societa per Azioni, Pavia, Italy Filed Sept. 7, 1961, Ser. No. 136,564 Claims priority, application Italy Feb. 10, 1961 20 Claims. (Cl. 192-442) This invention relates to an electrical control system for an operating machine.

A main object of the invention is to provide a novel and improved means for automatically controlling the entire operating cycle of a machine, for decreasing the speed of the machine shortly before the end of the cycle, and for finally stopping the machine at a well-defined position.

A further object of the invention is to provide an improved means for automatically controlling conventional mechanical drive members for operating the workholding clamp and for actuating the tool elements of an operating machine.

A still further object of the invention is to provide an improved means for automatically driving an operating machine through its cycle of operations at a constantly reduced speed.

A still further object of the invention is to provide an improved control system for an operating machine, said control system being provided with means to stop the machine in an emergency at any time with the possibility of either releasing or not releasing the work-holding clamp of the machine after stopping thereof, and with the possibility of restarting the machine either at normal speed or at reduced speed, either immediately or after having manually changed the angular position of a programming member of said machine.

A still further object of the invention is to provide an improved control system for an operating machine,'said system being provided with means to render inoperative one or more of the tools governed by the programming member of the machine so that they remain inactive during the operating cycle of the machine or during manual adjustment of said programming member.

The following description makes particular reference to an application of the device to a buttonhole sewing machine in which the work-holding clamp consists of a conventional presser foot adapted to hold the fabric on which the buttonhole is to be made in working position. The tools of the operating machine in this particular case are conventional knives adapted to cut the buttonhole and the upper and lower threads at the end of the operating cycle. v

The system of the present invention comprises a motor connected to the operating machine through a speed control assembly consisting of a clutch and an electromagnetic brake, a hand control for the starting of the machine, an operating-cycle programming member moved by a shaft of the machine, a speed regulating circuit for the machine, electric contacts controlled by said programming member and adapted to reduce the energization of 'the clutch and to connect said speed control assembly to said regulating circuit so as to effect'one or more reductions in speed distributing means having electric contacts which close responsive to each revolution of the main shaft of the machine, and a timed relay ice - energized by said programming member through said distributing means and of such a nature that is energization occurs only after the said programming member has switched said contacts in such a manner as to reduce the speed of the machine to a predetermined value, said timed relay being adapted to connect the electromagnetic brake to a full-energizing circuit for the brake in such a manner that the machine is automatically stopped at the end of the operating cycle at a predetermined position which depends on-the position of said distributing means with respect to the main shaft of the machine.

Further objects, advantages, and features of the present invention will become apparent from the following description and claims, and from the accompanying drawings, wherein:

FIGURE 1 is a wiring diagram of an improved electrical control system according to the present invention as applied to a buttonhole machine.

FIGURE 2 is a wiring diagram of a modified form of an electrical control system according to the present invention.

FIGURE 3 is a diagrammatic showing of the operational positions of the program member K on the switches X, Y and Z, and the buttonhole cutting knife n of the sewing machine. 1

FIGURE 4 is a schematic illustration of a buttonhole sewing machine of a type which can utilize the electric drive of the present invention.

Referring to the drawings, and more particularly to FIGURE 1, 10 designates a three wire supply line which is connected to an electric motor A, which drives a buttonhole machine C through a clutch B.

On the output shaft of the clutch B there is keyed a brake D. The clutch B and the brake D are of the electromagnetic type, for example, of the electromagnetic fluid type. Clutches and brakes of the electromagnetic fluid type are particularly well suited to the system of this invention since their excitation is adjustable over a wide range, they can be operated under reduced excitation conditions for long periods of time, and they are relatively quick-acting. However, it is to be understood that clutch B and brake D may be of any other suitable known type. V

The brake D and the clutch B are energized, as will be more fully described below, from the supply line 10 through a transformer 11 and a rectifier 12. The primary of transformer 11 is connected to

terminals

13 and 14 on two wires of line 10 on the load side of a main switch 15. The primary of a second transformer 18 is connected to terminals '16 and 17 on said two wires likewise on the load side of switch 15. The secondary of transformer 11 is connected to the input terminals of the rectifier 12 and the secondary of the transformer 18 is connected to the input terminals of a rectifier 19. The

secondary voltage of the transformer 18 is substantially greater than the secondary voltage of the transformer 11. For example, the secondary. voltage of transformer lfi'could be of the order of volts and that of transformer 11 could be of the order of 24 volts.

knives of the buttonhole machine. In particular, the

electromagnet E acts on the said mechanical elements in such a manner that when it is deenergized it causes the lowering of the presser foot into working position and makes the thread-cutting knife for the upper thread inactive; the thread-cutting knife for the lower thread, however, remains inactive until the electromagnet F is energized.

Connected between terminals and 21 on two of the wires of the supply line 10 is a circuit comprising a terminal 22, a terminal 23, a normally open switch GH, a. terminal 29, the winding of an electromagnetic switch H, and a terminal 25. The terminal 25 is connected to the terminal 21 by a common wire to which is also connected

terminals

33 and 26.

A line voltage, for example, 220 volts A.C., is present between

terminals

20 and 21.

Switch GH may be closed by actuating a pedal G. The switch GH is connected in parallel with protective means shown in FIGURE 1 as a resistor 27 and a capacitor 28 connected in series between

terminals

23 and 29.

As will be presently described, energization of the electromagnetic switch H causes energization of the clutch B and therefore starts the machine.

A terminal 24 is connected by a branch wire to terminal 22. Between the

terminals

24 and 26 is a first circuit branch leading to a terminal 30 and containing relay contacts NI; also connected between terminals 24 and 30 is a second circuit branch containing relay contacts LI and MI connected in series. The winding of a relay I is connected between terminals 30 and 26. Thus, relay I can be energized through the series-connected contacts LI and MI or through the contacts NI. As will be presently described, energization of the electromagnetic switch I controls the energization of the electromagnets E and F.

The contacts LI, MI and NI are controlled by the respective relays L, M and N, the circuits of which will be presently described. Normally, contacts MI are closed and contacts LI and NI are open.

A further branch circuit is provided between

terminals

22 and 33 comprising normally closed contacts HO, terminal 31, switch contacts 00, terminal 32, and the winding of an electromagnetic switch 0. A further branch circuit is provided between

terminals

32 and 33 comprising a terminal 34, contacts PP, terminal 35 and the winding of an electromagnetic switch P. Contacts HO are normally closed, and open responsive to the energization of electromagnetic switch H. Contacts 00 and PP are normally open and are closed responsive to the energization of the corresponding electromagnetic switches O and P, the said electromagnetic switches O and P being thus held energized.

Electromagnetic switch 0 is energized by actuating a push button Q which closes contacts QO connected in parallel with contacts 00 between the

terminals

31 and 32. Electromagnetic switch P is energized, subsequent to the energization of the electromagnetic switch 0, by actuating a push button R, which closes contacts RP connected in parallel with contacts PP between terminals 34 and 35.

As will be described below, the electromagnetic switch 0 controls the emergency stopping of the machine. The electromagnetic switch P, after the emergency stopping has been effected, controls the lifting of the presser foot of said machine.

The negative pole 36 of the rectifier 19 is connected to two terminals 1 and 2. The positive pole 37 of said rectifier is connected to a terminal 38.

Connected between the terminals 1 and 38 is the circuit controlling the position of the presser foot and of the thread-cutting knife for the upper thread. Starting from the terminal 1, one such circuit includes contacts 01 and II, the terminals 39 and 40, the switch contacts GE, the terminal 41, the electromagnet E, and the terminal 38. Connected in parallel with the series-connected contacts O1 and II are the contacts P1. Connected in parallel with contacts GE between terminals 40 and 41 is a protective circuit comprising the series-connected resistor 42 and capacitor 43. The contacts GE are normally closed and are opened responsive to the actuation of the pedal G. The contacts 01 and I1 are normally closed and open responsive to the energization of the respective electromagnetic switches O and I. The contacts P1 are normally open but are closed responsive to the energization of the electromagnetic switch P.

Connected between the terminals 2 and 38 is a circuit for controlling the action of the thread-cutting knife for the lower thread. This circuit comprises three parallelconnectcd sets of contacts H2, I2 and 02, connected between terminals 2 and 44, and the electromagnet F connected between terminal 44 and terminal 38. The three sets of contacts H2, I2, and 02 are normally open, and close responsive to the energization of the corresponding electromagnetic switches H, I, and 0.

Connected to the negative pole 45 of the rectifier 12 are the

terminals

3, 4, 5, 6, 7 and 8. Connected to the positive pole 46 of said rectifier are the terminals 3', 4', 5', 6', 7', and 8.

Connected between the terminals 3, 3' and 4, 4 are two switching circuits whose operation will be explained below.

Between the terminals 3 and 3', the switching circuit includes between terminal 3 and a terminal 47 respective parallel circuit branches, one of which includes a set of contacts H3 and the other of which includes seriesconnected sets of contacts 03, N3, and X.

The terminal 47 is connected to the terminal 3 through the winding of a relay N. Contacts H3 and N3 are normally open and contacts 03 are normally closed. Said contacts are controlled respectively by the electromagnetic switch H, the relay N and the electromagnetic switch 0. The contacts X are closed by a mechanical or electrical programming member actuated by the buttonhole machine. Said programming member may be of any known type, and in the accompanying drawings it is illustrated as a cam K rotating integrally with the buttonhole machine so as to rotate through one revolution with each buttonhole-making cycle.

The switch circuit connected between terminals 4 and 4' includes parallel-connected sets of contacts H4 and L4 connected between terminal 4 and a terminal 48, and the winding of a relay L connected between terminal 48 and terminal 4. The contacts H4 and L4 are normally open, and are closed responsive to the energization of the electromagnetic switch H and of the relay L, respectively.

The clutch B is connected between the terminals 5' and 5 through an energizing circuit comprising terminal 5', a terminal 49, the clutch B, a terminal 50, contacts L5, a terminal 51 and three branch circuits between terminal 51 and terminal 5. One of the branch circuits includes a set of contacts S1, a terminal 53 and a resistor 54. Another branch circuit includes the pole and one contact b of a set of contacts N5, the terminal 53 and the resistor 54. The remaining branch circuit includes the pole and contact a of contacts N5, and switch contacts S2.

The pole of contacts N5 normally engages contact b but moves into engagement with contact a responsive to the energization of relay N. Contacts L5 are normally open but close responsive to the energization of relay L. Under normal operating conditions of the buttonhole machine the contacts 81 are open, while the contacts S2 are closed. Said contacts S1 and S2 are displaced from their normal condition by-rnanually operating a switch control member S, as will be more fully described below, making it possible to operate the machine at a reduced constant speed.

Connected in parallel with clutch B between terminals 49 and 50 is a protective device, shown by way. of example as a rectifier 52.

The circuit comprising contact a, contacts S2 and terminal 5 constitutes the full-energizing circuit of the clutch B. The circuits which include terminal 53 and resistor 54, however, constitute reduced-energization cirsuits for clutch B. Said reduced energization circuits are provided for the purpose of causing slippage between the driving shaft and the driven shaft of the buttonhole machine, thus permitting the intervention of the speedregulating circuit of the machine. In the system illustrated in FIGURE 1, the speed regulating circuit of the machine is connected, in accordance with a preferred embodiment of the invention which will be described below, to the energizing circuit of the brake D. In this case, the reduced-energization circuit of the clutch includes the resistor 54 in the circuit which connects the terminal 53 to the negative pole 45 of the rectifier 12 through the terminal 5. FIGURE 2, on the other hand, illustrates an alternative embodiment wherein the speedregulating circuit of the machine is connected to the energizing circuit of the clutch B. In this second case, the reduced-energization circuit of the clutch B is combined, as will be explained further below, with the speed regulating circuit itself of the machine, and is therefore connected to the negative pole 45 of the rectifier 12 through the terminal 7.

The energizing circuit for the brake D is connected between a pair of terminals 55 and 56 connected respectively to the terminals 6 and 6'. A circuit branch between terminals 55 and 56 comprises contacts M6, contacts H6,

terminals

57 and 58, and the winding of the relay M. The

terminals

57 and 58 are respectively connected to a further terminal 59 through contacts 06 and Y. Terminal 59 is connected to a contact brush element 6t! forming part of a distribution assembly W comprising the collector rings 61, 63, and 65, mounted to rotate synchronously with the main shaft of the machine. The brush element 60 engages the ring 61 of the distribution assembly. The ring 61 is insulated except for a sector 62 thereof which is conductive and is electrically connected to the second ring 63, which is conductive over its entire periphery. Ring 63 is engaged by a contact brush 64 which is connected to the negative pole 45 of rectifier 12 through terminals 55 and 6.

Contacts M6 and 06 are normally open, and are respectively closed responsive to the energization of the relay M and the electromagnetic switch 0. Contacts H6 are normally closed, and are opened responsive to the energization of electromagnetic switch H. Contacts Y are normally open but are closed by the rotation of the cam K of the buttonhole machine.

The third collector ring 65 is conductive only over a sector 66 thereof, which is electrically connected to ring 63. The sector 66 has a greater angular width than the sector 62 and is angularly displaced behind sector 62 in the direction of rotation, as will be described further below. A brush 67 engages ring 65, said brush being connected to the terminal 56 through contacts HD, MD, terminals 68 and 69, brake D and a terminal 70. A protective device 71 is connected in parallel with the brake D between the

terminals

69 and 70, shown by way of example as a rectifier. Contacts HD are normally closed, opening responsive to the energization of electromagnetic switch H. Contacts MD are normally open, closing responsive to the energization of relay M.

The speed regulating means of the buttonhole machine comprises a generator T keyed to a shaft of the machine. Said generator acts to regulate the speed of the machine after the clutch B has been switched into its reducedenergizing circuit. Said generator can be connected to the energizing circuit of the brake D so as to control the excitation of the brake. Said generator T can, however, be connected also to the energizing circuit of the clutch in such a manner that its voltage opposes the voltage of the rectifier 12 and therefore controls the excitation of said clutch B.

It is also apparent that the case under consideration, the above two alternatives are substantially equivalent,

since the brake D and the clutch B, under conditions of reduced excitation of said clutch, cooperate to regulate the velocity of the driven shaft and therefore broadly constitute a unitary speed regulating means.

In the accompanying drawings there is shown a diagram of the speed regulating circuit of the buttonhole machine. In said diagram the circuit comprises, in addition to generator T, an amplifier, shown as a transistor U. Other circuit arrangements may be employed within the spirit of the present invention.

Starting from the terminal 7, the speed regulating circuit of the machine comprises two sets of contacts N7 and S3 connected in parallel with each other and in series with the collector 72 of a transistor U. Contacts N7 are normally closed, and open responsive to energization of relay N. Contacts S3 are open under normal operating conditions of the buttonhole machine and are closed responsive to operation of the switch S.

The base 73 of the transistor U is connected to the sliding contact 74 of a potentiometer 75 through the terminals 76 and 77, the resistor 78 and the

terminals

79 and 8%). Connected between the terminals 76 and 80, in parallel with resistor 78, are contacts H7 and Z in series. Connected in parallel with resistor 78 between

terminals

77 and 79 is a set of contacts 07. Contacts H7 are normally closed, and open responsive to the energization of the electromagnetic switch H. Contacts Z are normally closed, and are opened by the action of the cam K of the machine. Contacts 07 are normally open and are closed responsive to the energization of the relay 0.

Potentiometer 75 comprises a resistance winding 81 across whose terminals 83 and 84 is connected a capacitor 82. Also connected to said terminals 83 and 84 is the output of a tachometric generator T which is keyed to the driven shaft of the machine and whose field winding 35 is connected between the terminals 7 and 7' in parallel with a capacitor 86.

The winding 88 of a second potentiometer 87 has one terminal thereof connected to the terminal 84 and is shunted by a capacitor 89. In the arrangement of FIG- URE 1, the sliding contact 90 of potentiometer 87 is connected to the emitter 91 of transistor U through a terminal 92. In this arrangement, the speed regulating circuit of'the machine is connected to the excitation circuit of the brake D, and the connection is made by a conductor 93 connecting terminals 68 and 92. In the arrangement of FIGURE 1, the terminals 83 and 84 are respectively connected to the negative and positive poles of the generator T in such a manner that the energizing current of the brake D supplied by the generator T is in the same direction as the energizing current supplied by the retifier 12.

In the arrangement of FIGURE 2, the speed control circuit of the machine is connected :to the energizing circuit of the clutch B. The emitter 91 of the transistor U is connected to the aforementioned terminal 53 through a terminal 94 and a set of contacts M5 which open responsive to the energization of the relay M. The sliding contact 90 of the potentiometer 87, however, is connected to a terminal 95. Terminals 94 and 95 are respectively connected to the negative pole 96 and thepositive pole 97 of a rectifier 98, and are shunted by a resistor 99. The rectifier 98 is fed from the secondary of a transformer 100 whose primary is connected across two of the line wires of the supply line It) on the load side of main switch 15 at the terminals 101 and 162. In the arrangement of FIGURE 2, the terminals 83 and 84 are respectively connected to the negative and positive output terminals of the generator '1 in such a manner that the energizing current supplied to the clutch B by the generator opposes the energizing current supplied by the rectifier 12. g

In accordance with the present invention, two sets of

contacts

08 and 103 are connected between the terminals 8 and 8' in parallel with each other and in series with an

electromagnet V. Contacts

08 and 103 are normally open and are respectively closed responsive to the energization of the relay and by the actuation of a hand control I. The electromagnet V, when energized, acts on a pawl, not shown, in such a manner that the latter, by engaging the conventional buttonhole cutting knife of the buttonhole machine, prevents the knife from effecting the cutting of the buttonhole, controlled in a conventional manner by the cam K of the machine itself.

In FIGURE 4, the program member K, by means of the feeler a and the lever b, displaces the slide 0 along shaft d. To the slide c there is hinged work clamp f. The electromagnet E upon being energized raises the work clamp against the action of spring g and at the same time brings about the action of thread-cutting knife 11 of the upper thread-cutting member, which is schematically represented by blade i. Upon the raising of work clamp 1, blade i strikes against a stop I on the frame of sewing machine C and closes against a counterblade m fastened to work clamp f.

The buttonhole cutting knife 11 is guided vertically in the frame of the sewing machine C and is connected to a lever 0 having a feeler p which presses against the program member K. At the end of the cycle, the program member K causes the cutting action, because a pawl q controlled by electromagnet V prevents the action of the knife n when electromagnet V is not energized.

The thread-cutting knife r of the lower thread-cutting member is represented schematically by blade s which closes on a counterblade I when electromagnet F is deenergized.

The buttonhole machine operates as follows:

Pedal G is actuated so as to open the contacts GE. Electromagnet E is thus deenergized, causing the lowering of the presser foot of the machine into working position and making the thread cutting knife for the upper thread inactive. At the same time, the pedal G closes the contacts GH and energizes the electromagnetic switch H through the

circuit comprising terminals

20, 22. and 23, contacts GH, terminal 29, the winding of relay H, and

terminals

25 and 21. Electromagnetic switch H then closes contacts H2 and H3, and H4 and opens contacts H6, H7, HD and H0.

Closing of the contacts H2 causes energization of the electromagnet F through a circuit comprising terminals 36 and 2, contacts H2, terminal 44, electromagnet F, and terminals 38 and 37. Electromagnet F then actuates the drive members of the thread cutting knife in a direction to move said knife away from its working position.

Closing of the contacts H3 causes energization of the relay N through a circuit comprising terminal 3, contacts H3, terminal 47, the winding of relay N, and terminal 3'. Relay N closes contacts NI and N3, shifts the pole of switch N5 into engagement with contact a, and opens contacts N7. The closing of the contacts NI causes the energization of the electromagnetic switch I through a

circuit comprising terminals

20, 22 and 24, contacts NI, terminal 30, the winding of electromagnetic switch I, and

terminals

26, 25 and 21, so that the contacts 11 open and the contacts I2 close. The opening of contacts I1 will maintain the electromagnet E deenergized even when the pedal G subsequently closes the contacts GE. Similarly, the closing of contacts 12 will maintain the electromagnet F energized even when the deenergization of the electromagnetic switch H again opens the contacts H2. The closing of the contacts N3 prepares a holding circuit for the relay N through terminal 3, contacts 03, switch X, contacts N3, terminal 47, the winding of relay N, and terminal 3'.

Closing of the contacts H4 causes the energization of the relay L through a circuit comprising terminal 4, contacts H4, terminal 48, the winding of relay L, and terminal 4'. The relay L closes the contacts L1, L4- and L5. Closing of the contacts LI has the purpose of keeping the electromagnetic switch I energized even after the deenergization of the relay N has returned the contacts NI to open condition. The closing of the contacts L4 prepares a holding circuit for the relay L through terminal 4, contacts L4, terminal 48, the winding of relay L and terminal 4'. The closing of the contacts L5 causes full energization of the electromagnetic clutch B through a circuit comprising terminal 5, contacts S2, contact a and the pole of switch N5, terminal 51, contacts L5, terminal 50, clutch B, and terminals 49 and 5, and places the buttonhole machine in operation.

As soon as the machine begins operation its cam K closes the switch X, after which the pedal G is released, and upon returning to normal position, opens the contacts GI-I, thus deenergizing the electromagnetic switch H and again closing the contacts GE. Under these conditions, the electromagnet F is maintained energized through a circuit comprising terminal 2, contacts I2, terminal 44, the electromagnet F, and terminal 38; the relay N is maintained energized through a circuit comprising terminal 3, contacts 03, switch X, contacts N3, terminal 47, the winding of relay N, and terminal 3; relay L is maintained energized through a circuit comprising terminal 4, contacts L4, terminal 48, the winding of relay L, and terminal 4'.

When the operating cycle of the machine is almost completed, the cam K again opens the switch X so as to interrupt the holding circuit of the relay N and to thereby again open the contacts NI and N3, to shift the pole of switch N5 to contact b, and to close the contacts N7.

Under these conditions, in the form of the invention of FIGURE 1, clutch B is energized in series with resistor 54 through a circuit comprising terminal 5, resistor 54, terminal 53, contact b, the pole of switch N5, terminal 51, contacts L5, terminal 50, clutch B and terminals 49 and 5. Clutch B is thus under reduced excitation, which causes slippage of the driven shaft with respect to the driving shaft, and thus causes the machine C to slow down. At the same time, closing of the contacts N7 causes reduced energization of the brake D through a circuit comprising terminal 7, contacts N7, collector 72, emitter 91, terminal 92, conductor 93, terminals 68 and 69, brake D, and terminals 70, 56 and 6, the current furnished to the brake being proportional to the bias of the transistor U. The transistor U is biased by means of the generator T and the potentiometers 7S and 87.

Since contacts 07 are open, and since cam K has in the meantime opened the switch Z, the bias of the transistor U is reduced, since resistor 78 is placed in series with the base 73 of the transistor. The speed of the machine will be stabilized at a reduced value, depending on the positions of the sliding contacts 74 and 90 on the potentiometer resistors 81 and 38. If the machine tends to increase in speed, the output voltage of the generator T increases, whereby to increase the bias of the transistor U and to thus increase the excitation of the electromagnetic brake D.

Therefore, the brake D will counteract the increase in speed. On the other hand, if the machine tends to slow down, the output voltage of the generator T decreases, causing the bias of the transistor U to decrease, whereby to decrease the excitation of the brake and counteract the decrease in speed of the machine.

In the form of the invention of FIGURE 2, clutch B is energized with reduced current through a circuit comprising terminal 7, contacts N7, collector 72, emitter 91, terminal 94, contacts M5, terminal 53, contact 11, the pole of switch N5, terminal 51, contacts L5, terminal 50, clutch B, and terminals 49 and 5, the reduced excitation current being governed by the bias of the transistor U.

In this form also the speed of the machine is stabilized at a reduced value which depends on the position of the sliding contacts 74 and 93 on the potentiometers and e7. If the machine tends to increase in speed, the generator T increases its output voltage and therefore increases the bias of the transistor U, reducing the net current supplied to the clutch B and increasing the slippage between the driven and driving shafts, whereby to counteract the increase in speed of the machine. On the other hand, if the machine tends to slow down, the output voltage of the generator T decreases, decreasing the bias on the transistor and thereby increasing the net excitation current supplied to the clutch B, whereby to counteract the decrease in speed of the machine.

With a slight delay to allow the speed of the machine to stabilize itself to the reduced value, the cam K actuates a conventional mechanical device, not shown, for controlling the buttonhole cutting knife. Subsequently after the cutting of the buttonhole,the cam K again closes the switch Z and short-circuits the resistor 78 through the series-connected contacts H7 and switch Z, so that there is an increase in the bias on the transistor U. In the form of the invention of FIGURE 1, this increases the excitation of the brake D. In the form of the invention of FIGURE 2, this reduces the excitation of the clutch B. In both cases there is therefore obtained a second reduction in speed of the machine.

With a slight delay to allow the speed of the machine to stabilize to its new value, the cam K again operates and closes the switch Y. Closing of switch Y causes relay M to be energized through a circuit comprising terminals 6 and 55, contact 64,

ring elements

63 and 62, contact 60, terminal 59, switch Y, terminal 58, the winding of relay M, and terminals 56 and 6. Relay M is relatively slowacting and requires a predetermined time period of energization in order to operate. Relay M therefore operates only when the speed of themachine has dropped to a predetermined value corresponding to a definite time period of contact between brush 60 and the sector 62 of the collector assembly W. Sector 62 subtends an angle such as to permit relay M to operate only when the buttonhole machine has undergone said second reduction in Speed.

Operation of relay M causes contacts M6 and MD to close and contacts M1 to open. Furthermore, in the system shown in FIGURE 2, operation of the relay M also opens the contacts M5, so that when the brake D is actuated the clutch B is deenergized. This is necessary, since the braking of the machine would otherwise tend to increase the net current to the clutch because of the control action of transistor U. In the system of FIGURE 1, however, it is not necessary to deenergize the clutch B, since its energization, which is constantly reduced by the resistor 54 does not interfere with the stopping of the machine caused by the full energization of the brake D.

The closing of contacts M6 establishes a holding circuit for relay M comprising terminals 6 and 55, contacts M6, contacts H6,

terminals

57 and 58, the winding of relay M, and terminals 56 and 6, so that the relay M is maintained energized even when the brush 60 is no longer in contact with the sector 62 of the collector assembly W. Closing of the contacts MD causes the full energization of the brake D through a circuit comprising terminals 6 and 55, brush 64, ring 63, sector 66, brush 67, contacts HD and MD,

terminals

65 and 69, brake D, and terminals 76, 56, and 6'. The lag of the sector 66 of collector assembly W, with respect to sector 62 is calculated in such a manner as to guarantee that after the energization of relay M, the closing of the contacts MD will take place before the sector 66 reaches the position of the brush 67. Since the brake has a specific known time constant which does not vary, the machine will always be braked to come to rest gize the electromagnetic switch 0 through a

circuit comprising terminals

20 and 22, contacts HO, terminal 31, contacts Q0, terminal 32., the winding of electromagnetic switch 0, and

terminals

33, 26, 25, and 21. Energization of electromagnetic switch 0 closes contacts 00, O2, O6, O7, and O6, and opens

contacts

01 and 03.

The closing of the contacts 00 establishes a holding circuit for the electromagnetic switch 0. Closing of the contacts 02 maintains the electromagnet F energized through a circuit comprising terminals 36 and 2, contacts O2, terminal 44, electromagnet F, and terminals 38 and 37, so as to prevent the cutting of the lower thread by the operation of the associated thread-cutting knife. Closing of the contacts 08 energizes the electromagnet V through a circuit comprising terminal 8, contacts 68, electromagnet V, and terminal 8', and prevents the opera tion of the buttonhole cutting knife. The opening of the contacts 'Oll assures the deenergization of the electromagnet E, regardless of the position of the contacts 11 and GE, and therefore prevents the raising of the presser foot and the operation of the thread-cutting knife of the upper thread. The opening of contacts 03 deenergizes the relay N regardless of the position of switch X and therefore causes the pole of switch N5 to engage contact [2, whereby to establish the reduced-energization of clutch B. Finally, the closing of contacts 07 short-circuits the resistor 78, regardless of the position of switch Z, and therefore increases the bias on the transistor U so as to reduce the speed of the machine to the value required for the operation of relay M, whereupon the brake D can be energized through the circuit comprising terminals 6 and 55, the collector assembly W, contacts HD and MD, terminals 68 the machine.

As will be readily apparent, in the case of emergency stoppage, as above described, the machine always stops in a predetermined position of its main shaft.

After the emergency stopping of the machine has been effected, it may be desired to raise the presser foot. This is accomplished by depressing the push button R, so as to energize the electromagnetic switch P by a

circuit comprising terminals

20 and 22, contacts HO, terminal 31, contacts 00 in the holding circuit of electromagnetic switch 0, terminals 32 and 34, contacts RP, terminal 35, the winding of electromagnetic switch P, and

terminals

33, 26, 25 and 21. Energization of electromagnetic switch P closes contacts PP and P1.

The closing of contacts PP establishes a holding circuit for electromagnetic switch P so that the latter remains energized after release of the push button R. The closing of contacts P1 energizes the electromagnet E through a

circuit comprising terminals

36, 2 and 1, contacts Pl, terminals 39 and 40, contacts GE, terminal 41, electromagnet E, and terminals 38 and 37, thus causing the presser foot to be raised.

In order to resume the operating cycle from the point at which it was interrupted, it is merely necessary to again depress the pedal G so as to close the contacts GH. This energizes the electromagnetic switch H, opening the contacts HO and H6, thus deenergizing the electromagnetic switches O and P and relay M, restoring the operat ing condition of the machine.

For given jobs it may be necessary to operate the machine at reduced speed while maintaining all the other functions above described unchanged. This is tacts S3 connects collector 72 of the transistor U to terminal 7 regardless of the condition of the contacts N7.

In some cases it may be necessary that the buttonhole 11 be made without the action of the buttonhole cutting knife. Under these conditions the switch J is actuated to close the contacts 103, so that electromagnet V is constantly energized by a circuit comprising terminal 8, contacts 103, electromagnet V and terminal 8, and prevents the operation of said knife.

While certain specific embodiments of an electrical control system for an operating machine have been disclosed in the foregoing description, it will be understood that various modifications Within the spirit of the invention may occur to those skilled in the art. Therefore it is intended that no limitations be placed on the invention except as defined by the scope of the appended claims.

What is claimed is:

1. In combination, an operating machine adapted to perform a program of operations, an electric motor, an electromagnetic clutch connecting said motor to the machine, an electromagnetic brake operatively engaged with the machine, a programming member driven by the machine, means to fully energize said clutch to start the program of operations, means to simultaneously reduce the energization and to partially energize said brake at a predetermined point in said program, means to stabilize the machine speed at a reduced predetermined value immediately subsequent to said first-named predetermined point in the program, means to further reduce the speed of the machine at a subsequent point in the program, and means responsive to the reduction of the speed of the machine to another predetermined value to fully energize said brake and stop the machine.

2. In combination, an operating machine adapted to perform a program of operations, an electric motor, an electromagnetic clutch connecting said motor to the machine, an electromagnetic brake operatively connected to the machine, a programming member driven by the machine, means to fully energize said clutch to start the machine and initiate said program of operations, means operated by said programming member to reduce the energization of said clutch and at least partially energize said brake at a predetermined point in said prograb, whereby to reduce the speed of the machine, speedresponsive control means to stabilize the machine speed at a predetermined reduced value immediately subsequent to said predetermined point, means operated by said programming member to further reduce the speed of the machine, and means to fully energize said brake when the speed of the machine has been further reduced to another predetermined value.

3. In combination, an operating machine adapted to perform a program of operations, an electric motor, an electromagnetic clutch connecting said motor to the machine, an electromagnet brake operatively connected to the machine, a programming member driven by the machine, means to fully energize said clutch to start the machine and initiate said program of operations, means operated by said programming member to reduce the energization of said clutch and at least partially energize said brake at a predetermined point in said program, whereby to reduce the speed of the machine, speedresponsive control means to stabilize the machine speed at a predetermined reduced value immediately subsequent to said predetermined point, means operated by said programming member to further reduce the speed of the machine, an energizing circuit connected to said brake, a slow-acting relay having contacts connected in said energizing circuit, timed contacts operated by the machine, and means operated by said programming memher to energize said relay through said timed contacts at a further predetermined point in said program to fully energize said brake when the speed of the machine has been reduced to a further predetermined value.

4. in combination, an operating machine adapted to perform a program of operations, an electric motor, an electromagnetic clutch operatively connecting said motor to the machine in accordance with its degree of energization, an electromagnetic brake operatively engaging a driven element of the machine, a programming member driven by the machine, means to fully energize said clutch to start the machine and initiate said program of operations, means operated by said programming member to reduce the energization of said clutch and at least partially energize said brake at a predetermined point in said program, whereby to reduce the speed of the machine, speed governing means to stabilize the speed of the machine at a reduced value, means activating said speed governing means at said predetermined point in the program, means operated by said programming member to thereafter further reduce the speed of the machine, and means to fully energize said brake and to stop the machine at a predetermined position thereof when the speed of the machine has been further reduced to at least a predetermined further reduced value.

5. In combination, an operating machine adapted to perform a program of operations, an electric motor, an electromagnetic clutch operatively connecting said motor to the machine in accordance with its degree of energization, an electromagnetic brake operatively engaging a driven element of the machine, a programming member driven by the machine, means to fully energize said clutch to start the machine and initiate said program of operations, means operated by said programming member to reduce the energization of said clutch and at least partially energize said brake at a predetermined point in said program, whereby to reduce the speed of the machine, speed governing means to stabilize the speed of the machine at a reduced value, means activating said speed governing means at said predetermined point in the program, means operated by said programming member to thereafter further reduce the speed of the machine, a set of periodically closing timed contacts operated by the machine, the time of closure of said contacts depending on the speed of the machine, a slow-acting relay having contacts closing a predetermined time after the relay is energized, and means to fully energize said brake and stop the machine when the speed thereof has been sufiiciently reduced so that the time of closure of said firstnamed contacts is at least as great as the time required for the relay to close its contacts.

6. In combination, an operating machine adapted to perform a program of operations, an electric motor, an electromagnetic clutch operatively connecting said motor to the machine in accordance with its degree of energization, an electromagnetic brake operatively engaging a driven element of the machine, a programming member driven by the machine, means to fully energize said clutch to start the machine and initiate said program of operations, means operated by said programming member to reduce the energization of said clutch and at least partially energize said brake at a predetermined point in said program, whereby to reduce the speed of the machine, speed governing means to stabilize the speed of the machine at a reduced value, means activating said speed governing means at said predetermined point in the program, means operated by said programming member to thereafter further reduce the speed of the machine, a set of periodically closing timed contacts operated by the machine, the time of closure of said contacts depending on the speed of the machine, a slow-acting relay having contacts closing a predetermined time after the relay is energized, an energizing circuit controlled by said programming member and connected to said relay through said time contacts, and means to fully energize said brake and stop the machine when the speed thereof has been sufficiently reduced so that the time of closure of said first-named contacts is at least as great as the time required for said relay to close its contacts.

7. In combination, an operating machine adapted to perform a program of operations, an electric motor, an

electromagnetic clutch operatively connecting said motor to the machine in accordance with its degree of energization, an electromagnetic brake operatively engaging a driven element of the machine, a programming member driven by the machine, means to fully energize said clutch to start the machine and initiate said program of operations, means operated by said programming member to reduce the energization of said clutch and at least partially energize said brake at a predetermined point in said program, whereby to reduce the speed of the machine, speed governing means to stabilize the speed of the machine at a predetermined reduced value, means activating said speed governing means at said predetermined point in the program, means operated by said programming ember to thereafter further reduce the speed of the machine, a first set of periodically closing timed contacts operated by the machine, the time of closure of said contacts depending on the speed of the machine, a slowacting relay having contacts closing a predetermined time after the relay is energized, an energizing circuit controlled by said programming member and connected to said relay through said time contacts, a second set of periodically closing contacts operated by the machine and closing when the machine is in a predetermined position, and means to fully energize said brake through said second set of contacts and stop the machine substantially at said predetermined position when the speed thereof has been sufficiently reduced so that the time of closure of said first-named contacts is at least as great as the time required for said relay to close its contacts.

8. The structure of claim 6, and manually controlled means operable independently of said programming member for at times energizing said relay and for reducing the speed of the machine sufiiciently to allow said relay to close its contacts and to energize the brake.

9. The structure of claim 6, and manually controlled means operable independently of said programming member to maintain the clutch at reduced energization, whereby to operate the machine at reduced speed.

10. In combination, an operating machine, an electric motor, a electromagnetic clutch operatively connecting said motor to the machine in accordance with its degree of energization, an electromagnetic brake operatively engaging a driven element of the machine, means to at times fully energize said clutch to drive the machine, means to at other times reduce the energization of said clutch and partially energize said brake to reduce the speed of the machine, speed governing means to stabilize the speed of the machine at a predetermined reduced value, means to thereafter further reduce the speed of the machine, and means to fully energize the brake and to sto the machine when its speed has been reduced to at least a predetermined further value.

11. In combination, an operating machine, a electric motor, a electromagnetic clutch operatively connecting said motor to the machine in accordance with its degree of energization, an electromagnetic brake operatively engaging a driven element of the machine, means to at time fully energize said clutch to drive the machine, means to at other times reduce the energization of said clutch and partially energize said brake to reduce the speed of the machine, speed governing means to stabilize the speed of the machine at a predetermined reduced value, means to thereafter further reduce the speed of the machine, a set of periodically closing timed contacts operated by the machine, the time of closure of said contacts depending on the speed of the machine, a slow-acting relay having contacts closing a predetermined time after the relay is energized, and means to fully energize said brake and stop the machine when the speed thereof has been sutficiently reduced so that the time of closure of said first-named contacts is at least as great as the time required for the relay to close its contacts.

12. In combination, an operating machine, an electric motor, an electromagnetic clutch operatively connecting I said motor to the machine in accordance with its degree of energization, an electromagnetic brake operatively engaging a driven element of the machine, means to at times fully energize said clutch to drive the machine, means to at other times reduce the energization of said clutch and partially energize said brake to reduce the speed of the machine, speed governing means to stabilize the speed of the machine at a predetermined reduced value, means to thereafter further reduce the speed of the machine, a set of periodically closing timed contacts operated by the machine, the time of closure of said contacts depending on the speed of the machine, a slowacting relay having contacts closing a predetermined time after the relay is energized, an energizing circuit connected to said relay through said time contacts, and means to fully energize said brake responsive to the closure of the relay contacts when the speed of the machine has been sufficiently reduced so that the time of closure of said first-named contacts is at least as great as the time required for said relay to close its contacts.

13. In combination, an operating machine, an electric motor, an electromagnetic clutch operatively connecting said motor to the machine in accordance with its degree of energization, an electromagnetic brake operatively engaging a driven element of the machine, means to at times fully energize said clutch to drive the machine, means to at other times reduce the energization of said clutch and partially energize said brake to reduce the speed of the machine, speed governing means to stabilize the speed of the machine at a predetermined reduced value, means to thereafter further reduce the speed of the machine, a set of periodically closing timed contacts operated by the machine, the time of closure of said contacts depending on the speed of the machine, a slow-acting relay having contacts closing a predetermined time after the relay is energized, an energizing circuit connected to said relay through said time contacts, a second set of periodically closing contacts operated by the machine and closing when the machine is in a predetermined position, and means to fully energize said brake through said second set of contacts and stop the machine substantially at said predetermined position when the speed of the machine has been sutliciently reduced so that the time of closure of said first-named contacts is at least as great as the time required for said relay to close its contacts.

14. The structure of claim 11, and wherein the machine includes a work clamp device, means to move the work clamp device into operative position concurrently with the full energization of said clutch, and means controlled by said relay to move the work clamp device to inoperative position substantially simultaneously with the full energization of said brake.

15. The structure of claim 10, and wherein the machine includes movable tool elements, respective electromagnets controlling the positions of said tool elements, and means operating said electromagnets to move the tool elements in opposite directions respectively concurrently with the full energization of said clutch and substantially simultaneously with the full energization of the brake.

16. The structure of claim 10, and wherein said speed governing means includes a circuit containing at least one resistor, and wherein said means to further reduce the speed of the machine comprises means to short-circuit said resistor.

17. The structure of claim 10, and wherein said brak is provided with an energizing circuit including a transistor having a biasing circuit including a resistor, and wherein said means to further reduce the speed of the machine comprises means to short-circuit said resistor.

18. The structure of claim 10, and wherein said speed governing means includes a generator driven with the machine, and means to control the energization of the 15 brake in accordance with the output voltage of the generator.

19. The structure of claim 10, and wherein said sp d governing means includes a generator driven with the machine, and means to control the energization of the clutch inversely in accordance with the output voltage of the generator.

20. The structure of claim 10, and wherein said speed governing means includes a generator driven with the machine, and wherein said clutch is provided with an energizing circuit including a transistor, a source of reference voltage, and means to control the bias of the tran- 16 sistor in accordance with thedifference between the output voltage of said generator and the reference voltage.

References Cited in the file of this patent UNITED STATES PATENTS 2,816,635 Danly et al Dec. 17, 1957 2,906,217 Myska Sept. 29, 1959 2,920,221 Schwab Jan. 5, 1960 10 2,970,557 Schwab et a1. Feb. 7, 1961 3,025,444 Myska Mar. 13, 1962