US2032107A - Motor control system - Google Patents

Description

Feb 25, 1936. R. M. BAYLE 2,632,107

MOTOR CONTROL SYSTEM Filed Ma rch 24, 1951 Fig.1.

F192. Z 12 :2 m

WITNESSES: 5 INVENTOR W- V Russell M. Bayle BY I W Patented Feb. 25, 1936 UNITED STATES PATENT OFFICE MOTOR CONTROL SYSTEM Russell M. Bayle, Wilkinsburg, Pa, assignor to Westinghouse Electric .2 Manufacturing Compally, a corporation of Pennsylvania Application March 24, 1931, Serial No. 524,807

16 Claims. (01.172-239) what are commonly known as soaking pits, which are heated in any suitable manner until the ingots have reached the desired uniform temperature. The soaking pits, which are usually located in rows in the soaking-pit building, are provided with motor-actuated doors or covers, usually controlled by the operator of the crane which is utilized to insert the ingots into the pits and to 2 remove and place them upon an ingot buggy, or any other suitable device, to be transferred to the roll tables of the mill.

Heretofore, the control of the soaking-pit motors from the crane required the use of physical electrical connections between the crane and the motor-controller associated with each motor and located on the floor of the soaking-pit building.

The object of my invention, generally stated, is to provide for controlling the operation of a soaking-pit motor or motors from a moving or travelling crane without employing physical electrical connections between the crane at any part of the stationary motor-controller.

The object of my invention, more specifically stated, is to provide for selectively controlling the operation of a plurality of soaking-pit motors from a moving crane through the agency of photoelectric or light-sensitive devices.

Another object of my invention is to provide for initiating, and thereafter selectively controlling the direction of, the operation of a soakingpit motor from a moving crane in response to the successive flashes of a light source carried by the crane and controlled by the crane operator.

Other objects of my invention will become evident from the following detailed description, taken in conjunction with the drawing, in which,

Figure 1 is a diagrammatic view of a control system embodying the principal features of my invention, and

Fig. 2 is a general plan view, showing a single row of soaking pits and a travelling crane, together with the cover-actuating motors and various parts of the system shown in Fig. 1.

Referring now to the drawing, and particularly which this is done, is to place the ingots into to Fig. 2, there is illustrated a plurality of soaking pits I, 2, 3 and 4 extending across the floor of the soaking-pit'building. A track 5, extending along the side of the building, is provided for carrying an ingot buggy 6, which may be used 5 to convey the heated ingots from the soaking pits to the roll tables of I the rolling mill, (not shown). A travelling crane I, carried by suitable rails 8 and 9, is provided for lifting the ingots into and out of the various soaking pits.

As will be observed, the soaking pits are provided with doors or covers I I which may be actu ated to their open and closed positions by any suitable means, such, for example, as electric motors 12, which may be connected to their respective covers H in any desired manner.

Referring now to Fig. 1 of the drawing, there is shown a single soaking-pit motor [2 and its controller which are located on the floor of the soaking-pit building. In this instance, it has been deemed unnecessary to illustrate, in detail, more than one of the soaking-pit motor controllers since they are identical in construction, regardless of the number used in any one installation.

Each of the soaking-pit motors l2 comprises an armature l3 and a field winding l4 which may be energized from any suitable source of directcurrent power, illustrated, in this instance, by line conductors l5 and I 6.

Reversing switches l1 and I8 and a line switch I9 are provided for connecting the motor l2 to the power source to efiect its operation in either direction to open or close the soaking-pit cover.

A starting or plugging resistor 2| is provided for controlling the armature current of the motor during acceleration and plugging periods. The eifectiveness of the resistor may be varied by switches 22 and 23, which, in this instance, are controlled by time- delay relays 24, 25 and 26, in a manner which will be described more in detail hereinafter.

In order. that a more comprehensive understanding of the features of my invention may be obtained, a detailed description of the operation will now be given.

In this embodiment of the invention, provision is made for controlling each of the soakingpit motors l2 from the floor of the soaking-pit building, as well as from the moving crane. In order to accomplish this, each motor-controller is provided with a master switch 21, of any suitable type, which may be manually operated to control the operation of the reversing switches l1 and. I8 and the line switch l9 when it is desired to effect an opening or a closing operation of the soaking-pit cover from the floor of the soakingpit building without utilizing the crane control. As shown, the master switch 2? is provided with a movable segment 28 and a plurality of contact fingers 29 to 32, inclusive.

The operation of the soaking-pit motor i2 is also controlled, in accordance with the movements of the soaking-pit cover, or door, through the operation of suitable limit switches and 3 3, which are actuated to their circuit-opening positions only when the door or cover is actuated to-its open and its closed position, respectively. If the cover is closed, the limit switch 83 will be in the closed position and the limit switch 35 in the open position. As soon as the cover starts to open, the limit switch 34% closes, and the limit switch 53 remains closed until the cover reaches the full-open position.

In order to condition the motor-controller for operation, either from the floor of the soakingpit building or from the crane, the master switch 21 may be actuated to the off or reset posi-= tion, as shown, which establishes an energizing circuit for the low-voltage relay 35. This circuit extends from line conductor 85, through conductor 36, contact fingers 29 and tit-bridged by the segment 28coil of the low-voltage relay 35, conductor 37, neutralizing windings N of the timedelay relays 26 and 38 and conductor 55, to the line conductor l6.

Upon the closure of the low-voltage relay 55, the control conductor M is energized and remains connected to the line conductor i5 through conductor 35, contact finger 35 and the contact members of the low-voltage relay 35 until this relay becomes deenergized or a reduction in line voltage effects its operation.

When the control conductor 5! becomes energized, the magnetizing windings M of the timedelay relays 25, 25 and 38 become energized to effect the actuation of their respective relay armatures to their closed positions, thereby, opening the contact members 25a, 25a. and 38a. The magnetizing winding M of the time-delay relay 26 is connected across a section Zla of the starting resistor 2| by means of conductors 52 and 53, as shown, and is not energized until the motor circuit is established.

In order to control the energizing circuit for the reversing switches I! and i8 and line switch It, a relay M is provided which will be referred to herein-alter as the control relay.

In order to provide for controlling the operation of the control relay 45, that is associated with each soaking-pit motor controller, from the operators cab of the crane or conveyor, without the use of physical electrical connections between the crane and each controller, light-responsive control devices 45 comprising, generally, a photoelectric cell it, a grid-glow tube 5'8 and a telephone relay t8 are utilized.

As shown, the anode t9 and cathode 58 of the grid-glow tube 51 are connected in series-circuit with the operating winding, of the telephone relay 48 and the secondary winding 59 of the potential transformer 52. The primary winding 53 of the transformer is connected across a source of alternating-current power which may be illustrated, in this instance, by conductors 541 and 55.

The photo-electric cell 56 is connected to the grid 55 of the grid-glow tube 51 and functions in a well known manner, when a light is brought before it, to reduce the resistance of the gridglow tube sufficiently to permit current to flow aoeaior through the operating winding of the telephone relay 68 to efiect its operation.

In order to control the operation of the lightresponsive control device :35 from the crane, a light source, comprising a plurality of electric lamps 51, is provided. The lamps 51 may be carried on the crane in any suitable manner and energized from the crane power rails 58 and 59, as shown. The lamps 5'! may be conveniently mounted upon the crane by utilizing a box, or other container, rectangular in shape, having suitable openings provided in one side thereof and opposite each lamp in order that the rays from all the lamps may be directed in the same general direction. The light box may be located upon the crane in somewhat the general position shown in Fig. 1 in order that it shall be positioned directly in front of each of the light-responsive control devices as the crane moves into position over each of the soaking-pits.

It will be readily understood that the single light source may be utilized to control the operation of any number of soaking-pit motor controllers by so positioning the light-responsive control devices 35 along the crane runway that the light source shall be carried directly in front of each of the photoelectric cells as the crane moves back and forth over the soaking-pits.

The energizing circuit for the control lamps 51 may be controlled in any suitable manner, as, for example, by means of a switch 60, which may be a manually-operable push-button or a footoperated switch carried in the operators cab of the crane.

As will be readily understood, each time the control lamps 51 are flashed, the telephone relay 58 is actuated to its closed position to establish an obvious energizing circuit for the control relay 55.

In order to provide for selectively controlling the energization of the reversing switches I1 and G8 to control the direction of operation of the motor l2 in response to successive flashes of the control lamps 5'1, a transfer relay (ii is utilized.

In this embodiment of the invention, the transfer relay is illustrated as comprising a pivotallymounted beam 62 carrying movable contact members 63, 65, 55 and 65, disposed to engage fixed contact members 6i68 and 69l0, respectively. The relay is provided, with operating electro-magnets H and 12 and a biasing spring 62a, for controlling the movements of the beam 62. Each pair of movable contact members 63-54 and 6566, is connected to the beam 62 by means of spring connectors 62b which function to hold the lower contact members 66'|5 and 6468 into engagement to maintain their respective operating electro-magnets eiiective until the beam has been moved to slightly beyond its dead-center position where the biasing spring 620. becomes effective to actuate the beam to the opposite position after the lower contact members have become disengaged.

When the control relay. 4:2 is energized in response to a momentary fiash of the control lamps 51, an energizing circuit is established for the forward reversing switch [8 and line switch l9 which may be traced from the energized conductor lL'through the upper contact members of the control relay at, contact members 63 and 61, limit switch 33, conductor I3, the winding of the reversing switch i8, conductor l4 and the winding of line switch 19, to the line cenductor l5.

An energizing circuit for the motor i2 is thereby established, which extends from line conductor I5, through the field winding I4, contact members I8a, armature I3, contact members I8b, resistor 2| and contact-members a of the line switch I9, to the line conductor I6, which initiates the operation of the motor to actuate the soaking-pit cover toward the open position.

The motor is then accelerated to full speed through the functioning of the time- delay relays 24, 25 and 26. Since the accelerating control illustrated, forms no part of the present invention and any other suitable arrangement may be used, it has been deemed unnecessary to set forth a detailed description of the theory of operation of the relays as they are of the same kind and func tion in the same manner, as the relay covered by Letters Patent No. 1,753,983, granted to W. G. Cook, April 8, 1930.

As described hereinbefore, when the control conductor 4| was energized, in response to the closure of the low-voltage relay 35, the magnetizing coils M of the time- delay relays 24 and 25 became energized through a circuit extending from conductor 4|, through conductors 15 and 16, where the circuit divides, one branch extending through the magnetizing coil M of the relay 25, conductor 11, contact members d of the reversing switch I1, and conductors 18, 19 and 40, to line conductor I6, and the other branch extending, through the magnetizing windings M of relay 24, conductors 80, contact members d of the reversing switch I8 and conductors 19 and 40, to the line conductor I6.

The energization of these windings causes the contact members 24a and 25a to be opened. When the reversing switch I8 is actuated to the closed position, its contact members d are opened, thereby interrupting the energizing circuit for the magnetizing winding M of the relay 24. After a predetermined time delay, determined by the setting of the relay adjustment, the armature opens to close contact members 24a and establish an operating circuit for the switch 22 which extends from the conductor 4|, through conductor 8|, winding of the switch 22, conductor 82, contact members 24a, conductor 11, contact members d of the reversing switch I1 and conductors 18, 19 and 48 to line conductor I6. The operation of the switch-22 is efiected to shunt section 2Ia of the starting resistor 2| to increase the speed of the motor I2.

As described hereinbefore, the magnetizing coil M of the time-delay relay 26 is connected across the section 2|a of the starting resistor 2| and,

consequently, becomes energized to efiect the 1 operation of the armature and the opening of its contact members 28a when the motor circuit is established. When the resistor section 2Ia is shunted by switch 22, the magnetizing coil M becomes deenergized and, after a definite time delay, the armature swings open to efiect the closure of contact members 26a, thereby establishing an operating circuit for the second shunting switch 23. This circuit extends from the conductor 4|, through contact members 25a, the winding of the switch 23, conductor 82, contact members of the reversing switch I1 and conductors 18, 19 and 40 to line conductor IS. The closure of switch 23 causes full line voltage to be impressed upon the motor for accelerating it to full speed in the cover-opening direction.

In order to control the operation of the transferrelay 6| to effect the operation of the reversing switches I1 and I8, alternately in response to successive flashes of the control lamps 51, auxiliary relays 83 and 84 are provided for controlling the energization of the operating magnets 1| and 12 of the transfer relay.

As will be observed, the windings of the auxiliary relays 83 and 84 are connected in parallelcircuit with the windings of the reversing switches I8 and I1, respectively, by means of conductors 85 and 86 and a common return conductor 81. Consequently, when the operating circuit for the reversing switch I8 is established, as described hereinbefore', the auxiliary relay 83 was operated to establish an energizing circuit for the electromagnet 1|.

This circuit may be traced from conductor I6, through conductor 81, contact members a of the auxiliary relay 83, contact members 18 and 86 or the transfer relay 6|, the winding of the electro-magnet 1|, conductor 88, contact members 38a of the time-delay relay 38 which is now.

shown. Consequently, the closure of auxiliary relays 83 and 84 cannot eifect the operation of the transfer relay 6| until the contact members a of the time-delay relay 38 are closed.

In order that the controller may be responsive to a single momentary flash of the control lamps 51, and thereby make it unnecessary for the crane operator to maintain the lamp circuit closed for any appreciable length of time, holding circuits are provided for the reversing switches I1 and I8 and line switch I9. These circuits are established by contact members 0 of the reversing switches I1 and I8 when their respective reversing switches are closed. In this instance, when the reversing switch I8 is energized and closed, the contact members 0 complete the holding circuit which extends from conductor 4|, through conductors 15 and 9|, contact members 0 of the reversing switch I8, conductors 92 and 93, contact members 1) of the auxiliary relay 84, which are now closed, limit switch 33, conductor 13 and windings of reversing switch I8 and line switch I9, to the line conductor I6, as previously traced. This holding circuit is completed as; soon as the reversing switch I8 closes, and maintains the established motor circuit when the control relay 44 is deenergized in response to the deenergization of the control lamps 51.

Auxiliary relays 83 and 84 also function to render the master switch 21 ineffective to reverse the motor connection after it has first been established by the crane operator. In the operation just described, the auxiliary relay 83 was energized and opened its contact members b to interrupt the energizing circuit for the reversing switch I1 which extends from thecontact finger 32 of the master switch, through conductors 94 and 95, contact members 1), limit switch 34 of the auxiliary relay 83 and conductor 86, to

ating electro-magnet TH being maintained by lower contact members 66 and it until the beam 62 is in the dead center position.

As will be readily understood, the operation of the transfer relay 6! is effected a predetermined time after the motor circuit is established and does not, in any way, interfere with the operation of the motor until the crane operator flashes the control lamps 51 the second time. If the crane operator wishes to reverse the operation of the motor ,to actuate the soaking-pit cover to the closed position before it has reached the full-open position, he may accomplish this operation by flashing the control lamps 51 to operate the control relay G4 in the same manner as described hereinbefore, which, in this instance, establishes an operating circuit for the reversing switch H and line switch I9 and interrupts the operating circuit for the reversing switch it.

The operating circuit established for the reversing switch ii may be traced from the energized conductor til, through contact members of the control relay i l, contact member 63, conductor 91, contact members and 69, which are now closed, limit switch 3 5, conductor 96, winding of reversing switch 87, conductor M and the winding of line switch I 9, to the line conductor E6.

The operating circuit for the reversing switch it, in this instance, is interrupted through the operation of the auxiliary relay 85 which is energized over a branch circuit extending from conductor 56, through conductor 86, the winding of relay B l and conductor 87, to the line conductor l6. The operation of the relay 8% interrupts the holding circuit for the previously energized reversing switch H8 at contact members b, and closes the energizing circuit for the operating electro-magnet l2, of the transfer relay Bl, at contact members a.

In this instance, the motor I2 is accelerated to full speed in the reverse direction, through the functioning of time-delay relays 25 and 26, the resistor shunting switches 22 and 23 having opened during the transition period. The magnetizing coil M of the time-delay relay 25 is deenergized through the opening of the contact members d, of the reversing switch ill and the contact members 25a are closed, after a predetermined interval of time, to establish an operating circuit for the shunting switch 22, which may be traced from the energized conductor 6!, through conductor ti the winding of switch 22, conductor 82, contact members 25a of the time-delay relay 25, conductor 80, contact members d of the reversing switch l8'which are now closed, and conductor 59, to the line conductor l5. Upon the closure of the shunting switch 22, the magnetizing coil M of relay 26 is shunted to cause this relayto close its contact members 26a, after a predetermined interval of time, to establish an operating circuit for the shunting switch 23. This circuit may be traced from conductor il, through contact members 26a, the windingof the switch 23, conductor 82, contact members 25a, conductor 80, contact members (1 of the reversing switch 18 and conductor I9, to the line conductor 56. a

In this instance, the time-delay relay 38 functions in exactly the same manner as described hereinbefore to delay the operation of the trans- 'fer relay 6i for a predetermined interval of time after the energizing circuit for the motor has established. When the relay 38 closes, the energizing circuit for the operating electro-magnet i2 is established, and the transfer relay 5i aoeaior is again operated to its original position, as shown in the drawing.

The auxiliary relays 83 and B l function, in exactly the same manner as described hereinbefore, to render the master switch 21 ineffective to energize the operating circuit for the forward reversing switch l8 while the motor is operating in the reverse direction under the control of the crane operator. This circuit extends from contact finger 3! of the master switch, through conductors 99 and 93, where it is interrupted at contact members b of the auxiliary relay B l.

As will be readily understood, if the motor i2 is permitted to operate until the soaking pit cover is in the full-open or full-closed position, the motor circuit will be interrupted through the functioning of the limit switches 33 and 34, which are operated as previously described. Therefore, if the crane operator wishes to open the cover with the controller in the position shown in the drawing, he merely flashes the control lamps 51 to establish the forward running circuit for the motor and permit it to operate until the limit switch 33 is opened by the cover when it reaches the fullopen position. Since the limit switch 34 is closed at all times, except when the cover is in the fullclosed position and the transfer relay 6i operates to the opposite position from that shown in the drawing, the cover may be actuated to the closed position by a second flash of the control lamp 5?,

in the same manner as described hereinbefore, where the motor was reversed before the cover had reached the full-open position.

Therefore, it is evident that my invention provides for selectively controlling any number of soaking-pit motors from a moving crane without employing physical electrical connections between the crane and the respective motors. Any number of rows of motors may be controlled in this manner by simply providing separate groups of control lamps for each row of soaking-pit motors or else making provision for shifting the position of the control lamps on the crane in order to control the difierent rows of photo-electric cells which would be necessary if more than one row of motors were to be controlled.

It is also to be understood that my invention is not necessarily limited to the control of soaking-pit-cover motors since it may be applied, in an equally advantageous manner, for operating stationary devices of any kind, such for example, as furnace doors and the like from a moving crane or conveyor.

It may be noted in conclusion, that, while the illustrated example constitutes a practical embodiment of my invention, I do not wish to limit myself strictly to the exact details herein illustrated, since modification of the same may be made without departing from the spirit of the invention as defined in the appended claims.

I claim as my invention:

1. In a control system, in combination, a plurality of motor-operated work devices, a source of power, a traveling crane associated with the work devices, a plurality of reversing switches for connecting the motor-operated work devices to the power source, means operable independently of the motor and including a light-responsive device for controlling the operation of the reversing switches, said means being disposed to effect a reversal of the motor-operated work device in response to successive operations of the light-responsive device regardless of the position of the work device, and a light source energizable at the will of an operator and carried by the crane for effecting the operation of the lightresponsive device, thereby to provide for efiecting predetermined operations of the work device without the use of physical electrical connections between the crane and the work devices.

2. In a motor-control system, in combination, a motor, a source of power for the motor, a plurality of switches for connecting the motor to the power source, means, including a control relay, for controlling the cnergization of the connecting switches to effect a reversal of the operation of the motor in response to successive operations of the control relay, a manually operable master switch for further controlling the operation of the connecting switches, means responsive to the operation of the control relay for rendering the master switch ineffective to connect the motor to the power source in the opposite direction after the control relay has been operated and light-responsive means for controlling the energization of the control relay. '3. In a system for selectively controlling the operation of a plurality of work devices having predetermined limits of travel from a moving crane comprising, in combination, a plurality of motors for actuating the work devices, a source of power for the motors, means associated with each motor and successively operable independently of the motor to connect the motor to the power source to effect its operation successively in opposite directions .of rotation regardless of the position of the work device within the travel limits, light-responsive means associated with each motor for initiating the operation of the connecting means and means carried by the crane and operable at the will of an operator to cause the light-responsive means to function when the crane moves to predetermined positions relative to the light-responsive means.

4. In a system for selectively controlling the operation of a, plurality of work devices from a moving crane comprising, in combination, a plurality of motors for actuating the work devices, a source of power for the motors, means including a light-responsive relay associated with each motor and mounted independently of the crane and operable independently of the motor to connect the motor to the power source, said means being disposed, when operated successively, to effect successive reversals of the motor regardless of the position of the work device, and a light box energizable' at the will of an operator and carried by the crane and effective, when the crane is moved to predetermined positions relative to connecting means associated with each motor, for effecting the operation of the connecting means.

5. In a motor-control system, in combination, a motor, a source of power for the motor, a plurality of reversing switches for connecting the motor to the power source, an energizing circuit for the reversing switches, a transfer relay operable to transfer the energizing circuit from one to the other of the reversing switches, a control relay for controlling the energizing circuit, means responsive to the operation of the control relay for effecting the operation of the transfer relay, and means responsive to operation of the reversingswitches for delaying the operation of the transfer relay for a predetermined time interval after the motor has been energlzed in either directiomand means for controlling the'operation of the control relay.

.6. In a motor-control system, in combination, a motor, a source ofpower for the motor, a plurality of reversing switches for connecting the motor to the power source, an energizing circuit for the reversing switches, a transfer relay successively operable to at will alternately transfer the energizing circuit from the one to the other of the reversing switches, means including a control relay for controlling the energizing circuit of the reversing switches and for operating the transfer relay alternately in opposite directions, means including a light-responsive relay for controlling the energization of the control relay, and a light source disposed to be associated with the means including the light-responsive relay for eflecting its operation to selectively initiate and control the direction of operation of the motor.

7. 'Ilhe combination with a plurality of motoractnated work devices and a moving crane associated with the work devices, of a source of power for the motors, a plurality of reversing switches for connecting each motor to the power source, a lamp box carried by the crane and disposed to function as a light source to direct light rays in a predetermined direction, means mounted on the crane for controlling the energization of the lamp box, and means, including a lightresponsive relay device and a selecting relay associated with each motor-actuated work device and operable independently thereof for selectively controlling the energization of the reversing switches, said means being disposed to alternately initiate the operation of and effect a reversal of, any one of the motors in response to successive flashes of light from the lamp box regardless of the positions of the work device.

8. In a control system, in combination, a motor operated device having predetermined limits of travel, conductors for connecting the motor to a power source, switch means operable to connect the motor to the conductors to effect its operation in either a forward or a reverse direction, limit switches operable to disconnect the motor from the power source at the limits of its travel and means including a light-responsive relay device for controlling the operation of the switch means, said means being successively operable independently of the motor to alternately initiate the functioning of the motor in opposite directions independently of the limit switches without necessitating the completion of a cycle of movement in either direction.

9. In a control system in combination, a motor operated device having predetermined limits of travel, circuit means for connecting the motor to a power source, switch means successively operable to alternately connect the motor to the power source in opposite directions to successively effect its operation in either a forward or a reverse direction, a limit switch associated with each direction of operation of the motor-operated device and operative to disconnect the motor from the power source when the travel limit is reachedin either direction, said switch means being successively operable to at will control the operation of the motor independently of the functioning of the limit switches, means including a light-responsive device for controlling the operation of the switch means, and a light source disposed to effect the operation of the light-responsive device.

10. In a motor control system in combination, a motor, circuit means for connecting the motor to a power source, relay means operable to connect the motor to the power source to successively eifect its operation in either a forward or a reverse direction, a limit switch associated with each direction of operation of the motor and operative to disconnect it from the power source, said relay means being successively operable to control the operation of the motor independently of the functioning of the limit switches, control means connected to the relay means to provide a minimum time for the successive operation thereof, means including a light-responsive device for controlling the operation of the relay means, and a light source disposed to efiect the operation of the light-responsive device.

11. In a control system, in combination, a motor-operated device having predetermined limits of travel, a source of power for the motor, switch means operable to connect the motor to the power source to eiiect its operation in either direction, means including a control relay and a transfer relay successively operable to efiect the selective operation of the switch means to effect successive operations of themotor in opposite directions regardless of the position of the motor-operated device between its limits of travel, and means including a light-responsive relay for controlling the operation of the means including the control and transfer relays.

12. In combination, a plurality of electro-responsive Work devices, a movable conveying device associated therewith, a source of power, reversing switches for connecting the work devices to the power source for operation in opposite directions,

-a. control relay means including a transfer relay jointly responsive to the control relay and the reversing switches associated with each work device for controlling the operation of the reversing switches, said means being disposed on successive operation to alternately connect the work device for forward and reverse operation, light-responsive means for controlling the control relay and a light'source carried on the movable conveying device for causing the light-responsive means to function to initiate and control the direction of operation of the work devices.

13. In a control system, in combination, a plurality of electro-responsive work devices, a movable conveying device associated therewith and operable over a predetermined path of travel relative thereto; a source of power, light-responsive switch means for each work device successively v aosaior to become unresponsive to the operation of the manual switch associated therewith to cause the work device to operate in a direction opposite to that determined by the last operation of the light source.

14. In combination, a plurality of work devices, a motor for operating each work device, a source of power for the motors,'electro-responsive means associated with each motor successively operable to alternately connect the motor for operation in opposite directions, means including a lightsensitive device associated with each motor for successively operating the electro-responsive means in response to the successive flashing of a light thereon, and means rendered operable in response to each operation of the electro-responsive means to impose a predetermined time delay between the successive operations thereof, whereby the motor may be reversed only after the expiration of a predetermined time following the last reversal.

15. In a motor control system, in combination, a motor, a source of power for the motor, reversing switches for connecting the motor to the power source in opposite directions, a control relay for controlling the energization of the reversing switches, an auxiliary relay associated with each reversing switch and operable in response to the operation of the control relay to establish holding circuits for the reversing switches after the control relay opens, a transfer relay controlled by the auxiliary relays and operable to render the reversing switches and their associated auxiliary relays alternately responsive to successive operations of the control relay, and means for effecting successive operations of .the control relay.

16. In a motor control system, in combination, a motor, a source of power for the motor, reversing switches for connecting the motor to the power source in opposite directions, a control relay for controlling the energization of the reversing switches, an auxiliary relay associated with each reversing switch and operable in response to the operation of the control relay to establish holding circuits for the reversing switches after the control relay opens, a transfer relay controlled by the auxiliary relays and operable to render the reversing switches and their associated auxiliary relays alternately responsive to successive operations of the control relay, a time-delay relay operable in response to the closure of the reversing switches for delaying the operation of the transfer relay for a predetermined time after the operation of an auxiliary relay, and means including light-responsive means for controlling the operation of the control relay.

RUSSELL M. BAYLE.

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