US2103790A

US2103790A - Control system

Info

Publication number: US2103790A
Application number: US94822A
Authority: US
Inventors: Horace E Nason
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1936-08-07
Filing date: 1936-08-07
Publication date: 1937-12-28
Anticipated expiration: 1954-12-28
Also published as: DE743169C

Description

H. E. NASON CONTROL SYSTEM Dec. 28, 1937.

Filed Aug. 7. 1936 WITNESSES:

Patented Dec. 28, 1937 PATENT OFFICE CONTROL SYSTEM Horace E. Nason, Berwyn, 111., assignor to Westinghouse Electric & Manufacturing Company,

East Pittsburgh, Pa., vania Application August 7,

6 Claims.

This invention relates to control systems for paper mill drives.

In the manufacture of paper, it is usually made in webs that are too wide for-other industries. These wide webs of paper are usually cut or slit into secondary Webs of commercial size by transferring the wide web of paper from the paper machine past a roll carrying a slitter knife and adapted to rotate therewith to winder rolls upon which the secondary webs are wound. The slitter knife is carried by a roll driven at a speed approximating the speed of the winder rolls upon which the secondary webs are wound. If the speed of the roll carrying the slitter knife is reduced or falls below that of the winder rolls, the knife does not cut the paper, but instead tears it with the result that much spoilage of the paper is encountered during the slitting operation. Such conditions are more often found during the starting and stopping of the slitting operation. This is because the rolls on which the secondary webs are wound are often started before or ac- ,celerate at a faster rate than the roll carrying the slitter knife. Further, in stopping the slitter and Winder drive, the roll carrying the slitter knife sometimes stops before the winder rolls, with the result that the web tears as it is dragged past the stationary knife.

An object of this invention is to provide for starting and accelerating a slitter knifeto a predetermined speed before the winder rolls are started.

Another object of this invention is to provide for starting and accelerating a slitter knife to a predetermined speed before the winder rolls are started and for maintaining the slitter knife at a predetermined speed after the winder rolls are stopped.

A more specific object of this invention is the provision for transferring a slitter motor from an exciter to a generator upon the occurrence of predetermined voltage conditions, and to transfer the slitter motor from the generator back to the;

ing drawing, in which:

and

Figure 2 is a graph, the curves of which illustrate the control of the speed of the slitter and Figure l is a diagrammatic view of the control) system embodying the features of this invention.

a corporation of Pennsyl- 1936, Serial No. 94,822

winder motors obtained in accordance with the teachings of this invention.

Referring to the drawing and Fig. 1 in particular, this invention comprises a slitter roll l0 carrying a knife H for rotation therewith to slit a web of paper l2 as it is transferred from a roll of paper I4 to the winder rolls l6 and i8.

The slitter roll III is mechanically connected by means of a shaft 20 to a slitter motor 22 disposed to be electrically connected through a high resistance 26 to an exciter 28. Theslitter motor 22 is provided with a shunt field 24 disposed to be connected through a resistor to the exciter 28. The Winder rolls IE and [8 are mechanically con nected through shafts 3D and 32, respectively, to

compound motors

34 and 36, each of which is pro vided with a series field 38 and a shunt field 40. The

compound'motors

34 and 36 are disposed to be electrically connected to a generator 42 which is provided with a field winding 44.

In order to vary the excitation of the generator 42, a master rhecstat 50 is disposed to be connected in circuit relation with the field 44. The rheostat 50 may comprise any of the well known types of rheostats and is provided with a plurality of taps for connecting different portions of the rheostat in circuit with the field 44. The operation of the rheostat for varying the excitation of the generator and consequently the voltage delivered to the winder motors will be ex plained more fully hereinafter.

In order to transfer the slitter motor 22 from the exciter 28 to the generator 42, a relay 52 is so connected with its actuating coil in circuit with the generator 42 that upon the occurrence of predetermined voltage conditions the relay is actuated to disconnect the slitter motor 22 from the exciter 28 and to connect it to the generator 42. A time limit relay 54 of the type disclosed in Pat-- as No. 1,753,9 3, issued April 8, 1930 to w. G.

' "Cook, may her-"employed to insure the transfer the slitter/motor from the exciter to the gen- .ierator when the actuating coil of the relay 52 is energized.

In operation, the prime mover 48 drives the exciter 28 and the generator 42. ihe slitter motor is electrically connected to the exciter and accelerated to a predetermined speed. The shtter motor circuit may be traced from the exciter through the knife switch 56, conductor 58, adjustable regulating resistor 80, the shunt field 24 of the slitter motor 22, conductorsSZ and 84 back to the exciter. When the field oi the slitter motor is energized, the start button 66 may be actuated, closing a circuit which extends from the exciter through the knife switch 56, conductors 68 and 18, actuating coil 12 of a low voltage relay 14, conductors 16 and 18 and start button 66 to through the actuating coil 86 of relay 88 and the contact member I81 of the relay 52 to the energized conductor 64. When thus energized, the relay 88 is actuated to a circuit closing position in which contact member 98 connects the armature of the slitter motor22 to the exciter 28 to initially energize the slitter motor. The circuit thus established may be traced from the energized conductor 68 through resistor 26, contact member 98 of the relay 88, conductor 92, the armature of the slitter motor 22 and conductor 62 to energized conductor 68. The operating speed of the slitter motor 22 when connected to the exciter 28 is controlled by the resistor 26 which is in series with the armature of the motor. This predetermined speed is represented in Fig. 2 of the drawing by the ordinate 0-1.

When the relay 88 is actuated to connect the slitter motor 22 to the exciter 28, a circuit is also established by contact member 96 for energizing the magnetizing coil 96 of the time limit relay 54. This circuit extends from the energized conductor 68 through contact member 94 of the relay 88, magnetizing coil 96 of the time limit relay 54 and the resistor 91 in parallel therewith, to energized conductor 16. Since the magnetizing force of the coil 96 is greater than the neutralizing force of the neutralizing coil 98 of the time limit relay 54, the armature I88 is actuated to a position where a movable contact member I82 carried by the armature engages a contact member I84 and is held in a circuit closing position. The neutralizing coil 98 of the time limit relay 54 is provided for effecting a substantially constant dissipation of the residual magnetism of the core member of the relay from the maximum energized condition to zero for obtaining a prompt action of the armature I88 at any predetermined time interval in accordance with the teachings of the hereinbefore-identified Patent No. 1,753,983.

After the slitter 'motor 22 is started and accelerated to the predetermined speed, the

winder motors

34 and 38 may be connected to the generator 42 by actuating the bridging member I86 of the rheostat 58 to close a circuit through the actuating coil of contactor I32. As shown in the drawing, a movement of the bridging member I86 to the first tap of the rheostat establishes a circuit which may be traced from the energized conductor 68, through resistor I88, field 44 of the generator 42, bridging member I86, conductors I I8 and M2 to energized conductor 68. By connecting the resistor I88 in series with the field 84, any residual voltage of the generator 42 is bucked down as will be more fully described hereinafter.

A further movement of the bridging member I88 to the next tap of rheostat 58 causes segment II4 of the bridging member I86 to close a circuit which extends from the energized conductor 68 through stop button I28, actuating coil I22 of relay I24, conductor I26, bridging segment H4, contact member II5, conductors H8 and H2 to energized conductor 64. When this circuit is closed, actuating coil I22 of relay I24 is energized to actuate the relay I24 to a circuit closing position where its contact member I42 establishes a holding circuit for the relay. This circuit may be traced from the energized coil I22 through conductor II2 to energized conductor 64.

If the bridging member I86 is actuated to the third tap of the resistor 58, the segment.| I4 of the bridging member bridges conducting segments H6 and H8 to close a circuit which extends from energized conductor I26, through conductor I28, actuating coil I38 of contactor I32, contact member I36 of contactorv I32, and coil I38 of relay I48 to energized conductor 64. The energization of coil I38 of contactor I32 causes the contactor I32 to be actuated to a circuit closing position in which contact members I44 and I46 connect the

winder motors

34 and 36, respectively, to the arma re of the generator 42. In this position the cont; t member I48 of contactor I32 closes a circuit I hich may be traced .from energized conductor 68 through conductor I58, contact member I48, conductor I52 and actu .ating coil I54 of relay I56 to energized conductor 64.

circuit may be tracedfrom energized conductor 68 through contact member I58, conductor I68, field 54 of generator 42, rheostat 58, and conductor I62 to the energized conductor 68.

In order to increase the voltage generated by the generator 42, the rheostat 58 is adjusted to increase the strength of the field 44. As the voltage generated and delivered to the winder motors increases and consequently the speed of the

motors

84 and 56 approaches the predetermined speed of slitter motor 42, represented in Fig. 2 by the ordinate 0-1, actuating coil I59 of relay 52 is energized to actuate the relay to.an energized position. In this position the contact member I6I of relay 52 is in a circuit interrupting position and contact member I62 is in a circuit closing position. 6

When the contact member I6I is actuated to its circuit interrupting position, actuating coil 86 of relay 88 is de'energized and relay 88 drops to its deenergized position in which the

contact members

98 and 94 interrupt the circuits from the exciter to the armature of the slitter motor and from the exciter to the magnetizing coil 96 of the time limit relay 54, respectively. Because of the characteristics of the relay 54 a predetermined time limit is provided in which the contact members I82 and I84 engage after the contact member 94 interrupts the circuit to the magnetizing coil. This period of delay is suflicient to permit contact member I62 of relay 52 to close a circuit which extends from energized conductor 68 through the contact members I84 and I82, ar-

mature I88, conductor I64, actuating coil I68 of Since each of the motors is connected in circuit relation with the generator, the speed of the motors may be controlled by adjusting the master rheostat 50 to regulate the voltage generated by the generator 42. Since the margin of speed at a given armature voltage of the generator between the slitter motor and the winder motors as shown in Fig. 2 is fixed by the characteristics of the motors, the safety margin may be maintained over a given range of speed.

Upon a decrease in speed of the winder motors through an insertion of more of the rheostat 50 in series with the field 44 of the generator 42, the speed of the slitter motor is decreased proportionately to the speed of the winder motors. When the voltage generated decreases and the speed of the motors is lowered to the predetermined value, the actuating coil I58 becomes deenergized and the relay 52 returns to its deenergized position. As the relay 52 drops to its deenergized position, contact member I62 drops to a circuit interrupting position to interrupt the circuit to and deenergize the actuating coil I68 of relay I'I0. When the coil I68 is deenergized, relay "0 and its contact member I12 drop to a circuit interrupting position to disconnect the slitter motor from the generator. The deenergization of actuating coil I59 of relay 52 also permits contact member I6I of the relay to drop to a position where it establishes an energized circuit through the actuating coil 86 of relay 88 to actuate the relay to a circuit closing position in which contact member connects the slitter motor to the exciter. Thus as the voltage generated and delivered to the

winder motors

34 and 36 is further decreased, the speed of the slitter member 32 is maintained at the predetermined speed to cause the operation of the slitter knife I0 even though the winder motors stop.

In order to stop the winder motors, the bridging member I06 of the rheostat 50 is actuated to a position where the bridging segment I I4 bridges the segment H6 and contact member II5 of conductor IIO. In this position the circuit through the actuating coil I 30 of interlock I 32 is interrupted and the interlock I32 drops to its deenergized position in which the contact members I44 andI46 disconnect the

motors

34 and 36, respectively, from the generator 42. When the interlock I32 is in its deenerglzed position, the contact member I48 interrupts the circuit through the coil I54 of relay I56 causing relay I56 to drop to its deenergized position in which contact member I58 interrupts the circuit from the energized conductor 64 through the field 44 of the generator 42. When the interlock I32 is in its deenergized position, the contact member I36 closes a circuit as hereinbeiore explained, which extends from energized conductor I34 through the actuating coil I38 of relay I40 to energized conductor 64. The relay I40 is thus actuated to its circuit closing position in which contact members I16 and I18 connect resistors I80 and I82, respectively, in shunt circuit relation about the

motors

34 and 36 to provide dynamic braking therefor.

In stopping the

winder motors

34 and 36, the speed of the motors may be decreased by actuating the bridging member I06 of rheostat 50 to its initial position where a circuit through the high resistor I08 is completed, reversing the field and bucking down any residual magnetism of the generator. The field of the generator is thus reversed from the normal excitation direction when the winder motors are disconnected from the generator and for all initial starting operations of the system. By providing for reversing the field oi the generator, as described, the generator voltage is increased slowly in the proper direction as the rheostat 50 is cut out of the circuit by the bridging member I06 and a smooth starting operation of the

winder motors

34 and 36 is obtained.

When desired, the winder motors may be disconnected from the generator by actuating stop button I20 to its circuit interrupting position where it interrupts the circuit through the actuating coil I30 of the contactor I32. The opera. tion of the contactor I32 to disconnect the

winder motors

34 and 36 from the generator 42 and to close an energized circuit through relay I40 to connect resistors I80 and I82, respectively, in shunt circuit relation about the

winder motors

34 and 36 to provide dynamic braking therefor is the same as has been described hereinbefore.

The slitter motor 22 may be stopped at any time by depressing the stop button 84 to interrupt the circuit through the actuating coil I2 of relay I4 and to deenergize the actuating coil 86 of relay 88 to disconnect the slitter motor 2 from the exciter 28. e

In the operation of the control system as hereinbefore described it is evident that the slitter motor may be started and accelerated to a predetermined speed prior to the starting of the winder motors, and after the, stopping of the winder motors. By this control system an improved slitting operation is obtained by maintaining a definite predetermined minimum speed of the slitter knives. Further, it is seen that the speed of the slitter motor varies in accordance with the speed of the winder motors for all speeds above a predetermined minimum speed and that operation of the slitter motor is insured even after the winder motors have ceased to function. This invention provides against damage to the web of the paper through a failure of the slitter motor to maintain a, speed greater than that of the winder motors.

Although this invention has been described with reference to a particular modification thereof, it is to be understood that other and various modifications thereof are possible. This invention is, therefore, not to be restricted except insofar as is necessitated by the prior art and the scope of the appended claims.

I claim as my invention:

1. In a paper mill drive, a generator having a field winding, an exciter for the field winding, a slitter motor disposed to be connected to the exciter, a winder motor disposed to be connected to the generator, means for controlling the generator to control the voltage output therefrom, and means res;.onsive to predetermined voltage conditions for transferring the slitter motor to the generator to control the speed of the slitter motor with respect to the speed of the winder motor.

2. In a paper mill drive, a generator having a field winding, an exciter for the field winding, a. slitter motor disposed to be connected to the exciter, a. winder motor disposed to be connected to the generator, means for controlling the generator to control the voltage output therefrom, and means responsive to predetermined voltage conditions for transferring the slitter motor from the exciter to the generator to control the speed of the slitter motor with respect to the speed of the winder motor, the said means being responsive upon failure of the predetermined Voltage conditions to transfer the slitter motor from to the generator after the initial energization the generator to the exciter to maintain the operation of the slitter motor at a predetermined speed.

3. In a paper mill drive, a generator having a field winding, an exciter for the'fleld winding, a slitter motor disposed to be connected to the exciter, a winder motor disposed to be connected to the generator, means for controlling the excitation of the generator to control the voltage output therefrom and thereby control the speed of the winder motor, and means responsive to a predetermined voltage output of the generator for transferring the slitter motor from the exciter to the generator to control the speed of the slitter motor with respect to the speed of the winder motor.

4. In a paper mill drive, a generator having a field winding, an exciter for the field winding,

a slitter motor, means for connecting the slitter motor to the eirciter to initially energize the slitter motor and operate it to a predetermined speed, a winder motor disposed to be connected to the generator after the initial energlzation of the slitter motor, means for controlling the excitation of the generator to control the voltage output therefrom and thereby control the speed of the winder motor,'and means responsive to predetermined voltage conditions for transferring the slitter motor to the generator to control the speed of the slitter motor with respect to the speed of the winder motor.

5. In a paper mill drive, a generator having a field winding, a'n exciter for the field winding, a slitter motor, means for connecting the slitter motor to the exciter to initially energize the slitter. motor and operate it ,to a predetermined speed, a winder motor disposed to be connected of the slitter motor, means for controlling the excitation of the generator to control the voltage output therefrom and thereby control the speed of the winder motor, and means responsive to predetermined voltage conditions for transferring the slitter motor from the exciter to the generator .to control the speed of the slitter motor with respect to the speed of the winder motor, the said means being responsive upon failure of the predetermined voltage conditions to transfer the slitter motor fromthe generator to the exciter to maintain the operation of the slitter motor at a predetermined speed.

6. In a paper mill-drive, a generator having a field winding, an exciter for the field winding, 9. slitter motor, means for connecting the slitter motor to the exciter to initially energize the slitter motor and to operate it to a predetermined speed, a winder motor disposed to be connected to the generator after the slitter motor is initially energized, means for controlling the voltage output from thegenerator and thereby control the speed of the winder motor, means responsive to a predetermined voltage output for transferring the slitter motor from the exciter to the generator for increasing the speed of the slitter ,motor as the speed of the winder motor increases,

noaacjn E. NASON.