US1797969A - Control system - Google Patents

Description

March 24, 1931. A, MA Y 1,797,965

CONTROL SYSTEM 1 Filed June 22 192 Inv entom Leonid A. Um ansKX' by w/ mzm/ His Attovn ey Patented Mar. 24, 1931 UNITED STATES PATENT OFFICE LEONID A. UMANSKY, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK CONTROL SYSTEM Application filed June 22,

My invention relates to control systems, more particularly to control systems for a plurality of devices arranged for simultaneous operation on a length of material, such as rolling mills and like, and has for its object the provision of such a control system which is of simple construction and which is convenient and eflicient in operation.

Although it obviously has other applications, my invention is particularly useful 'in connection with rolling mills for bar metal materials.

A great proportion of bar metal is shaped into the desired form b passing the metal through rolling mills. t will be understood that these mills frequently comprise a number of consecutive rolls arranged so as to operate simultaneously on the metal to be shaped, 1

the metal being gradually brought to its finished form and size as it is run through the mill. The successive rolls of the mill are frequently driven by separate operating means and in order. to secure successful rolling it is very desirable to maintain a substantially constant speed ratio between these operating means.

In many such installations certain of the operating means areof a very small size as compare with the means operating the associated rolls. For instance, the operating means of the edging rolls of the mill is of relatively small size as compared with the main mill operating means. It is, therefore, very likely that the small edging roll operat- 85 ing means will be overloaded at times, and

in consequence it is very likely that the shaping operations will be detrimentally affected.

In one of its aspects my invention contemplates the provision of means for controlling the edging roll drive so that each of the above mentioned desirable features will be obtained. That is, a substantially constant s eed ratio will be maintained between the e ging roll drive and that of the associated rolls, and

further the edging roll drive will be protected from overloads.

In carrying my invention into effect in one form thereof, I provide s eed control means for the operating means or the edging rolls so that a substantially constant predeter- 1928. Serial No. 287,600.

mined speed ratio will be maintained between this operating means and the means operating the associated mill, that is, a substantially constant speed ratio will be maintained between the edging roll drive and the bar metal being fed through the mill. I further arrange my control system so that the edging roll drive will be protected from excessive loads.

For a more complete understanding of my invention reference should be had to the accompanying drawing in which the sin le figure is a diagrammatic representation 0 a system of control embodying my invention.

Referring to the drawing I have shown my invention in one form as applied to a direct current motor employed to drive the edgn rolls of a metal rolling mill. As shown, a direct current motor 10, provided with an armature 11 and a shunt field winding 12, is mechanically connected to drive the ed ing rolls 13. The edging rolls 13 serve to operate upon a bar of metal 14 which is passed through the edging rolls 13 and the main rolls 15 of the mill. A suitable source of direct current supply 16, is provided for the motor 10, both the armature 11 and the field winding 12 being supplied by the source 16. It will be understood that the shunt field 12 may be supplied from any suitable source which has a substantially constant voltage. A suitable starting controller 17 is provided for the motor 10. Any suitable means may be provided for driving the main rolls 15. As shown, a steam engine 18 is provided for this purpose, the steam engine 18 being either of the constant speed or of the adjustable speed type. The steam engine is shown mechanically connected by means of a belting 19 to drive the main rolls It will be understood that in the manufacture of bar metal and similar materials the metal is gradually brought to its finished size and shape by passing it through a series of rolls, and in order to secure successful rolling it is necessary to maintain a substantially constant speed ratio between the operating means of the various rolls. It will be further understood that the motor which drives the edging rolls is of very small size as compared with the operating means of the main rolls and therefore, this motor must be protected against excessive loads in order that continuous operation of the mill will be possible.

In order to effect these requirements I provide control means comprising a regulator 20 for controlling the speed of the motor 10, which is employed to drive the edging rolls, so as to cause the motor speed to vary with the speed of the main prime mover 18 in a substantially fixed ratio, and further to cause the motor to slow down under load so as to relieve it of excessive overloads. As shown, the regulator 20 comprises a pivoted bar 21, a coil 22 having its core connected to the bar 21 at one end thereof, and a coil 23 having its core connected to the bar 21 at a point intermediate its pivot and its other end. The pull of the coil 22 should be pro portional to the speed of the prime mover 18 and the pull of the coil 23 should be pro portional to the speed of the electric motor 10. In order to eflect these proportionalities suitable pilot generators 24 and 25 are pro vided, the generator 24 being mechanically connected so as to be driven by the steam engine 18 and the generator 25 being mechanically connected so as to be driven by the electric motor 10. The generators 24 and 25 are provided with separately excited fields 28 and 29' respectively, the fields 28 and 29 being conveniently connected in series with each other and being excited from the supply source 16. As shown, the coil 22 is connected across the armature 26 of the generator 2 1 so that its pull u on its core will be proportional to the v0 tage of the nerator 24 and consequently to the speed at which the steam engine drives the finishing rolls 15. Likewise, the coil 23 is connected across the armature 27 of the generator 25 so that its pull will be proportional to the speed at which the motor operates the edging rolls 13.

The regulator 20 operates to effect a variation in the strength of the field 12 of the motor 10 and thus a variation in its speed by operating directly upon a counterelectromotive force machine 30. The machine 30 is so arran ed in the circuit of the field 1.2 that the v0 tage generated by the machine 30 will oppose the line voltage impressed upon the field. The counterelectromotive force machine 30 is driven at a substantially constant speed by any suitable means such as a small direct current motor 31 connected across the armature circuit of the motor 10 so that "as long as the motor 10 is in operation the counterelectromotive force machine 30 will be in operation. The machines 30 and 31 are provided with separately excited fields 33 and 34 respectively, these fields being shown as supplied from the source 16. A suitable rheostat 35 is -rinterposed in the circuit of the field 12 whereby the speed of motorlO may be controlled by hand if desired.

A resistance 36 is inserted in series with the field winding 33 and is controlled by the regulator 20 so as to vary the strength of the field 33 and consequently the opposing effect of the counterelectromotive force machine 30 upon the field winding 12. As shown, the regulator 20 is provided with contacts 37 connected across the resistance 36 so that when the contacts are open the resistance will be inserted in the field circuit of the machine 30 and when the contacts are closed the resistance will be short circuited. The proportion of the time that the contacts 37 are closed to the time that these contacts are open will determine, as is. well known, the average value of the field current of the machine 30 and therefore, the counterelectromotive force of the machine 30, and finally the speed of the motor 10. It w1ll be evident that the proportion of time that the contacts will remain open or closed will depend upon the relative values of the currents that energize the coils 22 and 23 and in consequence, upon the relative speeds of the machines 18 and 10, for a. given setting of the speed ratio adjusting rheostats 42 and 43.

\Vhen the regulator is once adjusted, should the speed of the motor 10 rise above the desired value, the coil 23 will overbalance the coil 22 and the contacts 37 will be held in their open position thus inserting the resistance 36 in the circuit of the field 33. As a result of this operation, the effective excitation of the machine 30 will be reduced, and therefore, the field strength of the motor 10 will be increased. The motor 10 will then slow down until when the speed is less than the speed necessary to maintain the desired ratio, the coil 22 will overbalance the coil 23 and the contacts 37 will be closed to short circuit the resistance 36. As a result of this operation, the excitation of the. machine 30 will be increased which results in a decrease in the field strength of the motor 10. The speed of the motor 10 will then increase until it is greater than the desired speed and the coil 23 will again overbalance the'coil 22 and the contacts 37 will be opened to reinsert the resistance in the field circuit of the machine 30. The motor 10 will then slow down and the cycle of operation will be repeated as previously described. The regulator 20 will thus have a vibratory motion alternately short circuiting and inserting the resistance 36 in the field circuit of the machine 30. As the contacts 'rapidly vibrate, the effective resistance in the field circuit of the machine 30 and consequently the strength of the field 12 of the motor 10 will depend upon the proportion of time that the contacts are in their open position,-' and the motor 10 will be caused to operate at a constant speed, assuming the prime mover.

18 to be operating at a constant speed, or its speed will be changed as the speed of the prime mover 18 is changed so that the ratio between these speeds will be substantially constant. The regulator may be provided with a damping dash pot 38, whose damping effect may be varied as desired by means of its valve 39.

An anti-hunting coil 40 may be provided as is customar with this type of vibratory regulators. Tiis coil 40 has its core connected to operate upon the upper of the contacts 37. As shown, the coil 40 is connected across the armature of the machine 30 so that after the contacts 37 are closed the momentary increase of the armature voltage of the machine 30 due to the increase in its field excitation will cause the coil 40 to immediately open the contacts 37 and will thereby limit the excessive field weakening of the motor 10 and prevent, therefore, the hunting action of the regulator. The pull exerted by the coil 40 is balanced by a spring 41, which spring returns the upper contact 37 to its original position upon the decrease in the current flowing through the coil 40.

' It is desirable at times to change the speed ratio to be maintained between the motor 10 and the prime mover 18 and in order to change this speed ratio the setting of the regulator 20 is accordingly adjusted. This ad ustment of the regulator 20 is efi'ected by means of the rheostats 42 and 43. The rheostat 42 is inserted in the circuit of the coil 22 and the rheostat 43 is inserted in the cirdifferent speed ratio. 'As shown, the rheostat 43 is mechanically connected to the rheostat 42 and is so arranged that its effective resistance will be varied inversely as the effective resistance of the rheostat 42 is varied,.

and simultaneously therewith. This ,mechanical connection is effected for instance by providing each of the movable elements of the rheostats 42 and 43 with a gear member 44. A suitable shaft 45 is arranged to operate between the rheostats, the shaft being provided with worm gears 46 which mesh with the gears 44 so that when the shaft is turned, motion will be imparted to each of the movable elements whereby the effective resistances of the rheostats will be varied, the effective resistance of the rheostat 43 being increased when the effective resistance of the rheostat 42 is decreased, and vice versa. The shaft 45 is shown provided with a suitable crank 48 geared thereto whereby it may .be conveniently operated.

gine 18 driving the mill, and therefore, since' these two machines are working simultaneously on the same piece of metal, it is likel that the motor 10 may be excessively over oaded at times, particularly when feeding the bar metal from the edging rolls 13 to the main mill rolls 15 in the starting operation, even though the s eed ratio is held substantially constant. hus in the starting operation, it will be understood that this regulator 20 will be adjusted so as to maintain a substantially constant speed ratio between the steam engine 18 and the edging roll motor. Moreover, it will be understood that in the starting operation the bar metal 14 will be fed from the edging rolls 13 to the main mill rolls. Thus, in the event the setting of the regulator to be such that the motor 10 be operating at too high a speed, the motor will be overloaded excessively when the-bar is fed into the mill rolls 15 since under such circumstances the edging roll the motor so as to cause the motor to tend to slow down under load and thereby relieve it from excessive loads. As shown, the motor 10 is provided with a series field 50 which ordinarily would tend to cause the motor to slow down. It will be obvious however, that the action of the regulator 20 must be modified responsively to the load since otherwise the regulator would tend to counteract the effect of the series field and tend to cause the motor to run at a speed as determined by the speed ratio setting of the regulator. In order to cause the regulator to so respond to the strength of the field 50,it is provided with an operating coil 51 the pull of which is in this case cumulative with that of the coil 23.

The coil 51 is connected across the series field 50 and therefore, the pull exerted by the coil 51 will be proportional to the current in the armature circuit of the motor 10. Therefore if the motor is heavily loaded, the coil 51 will increase the pull exerted by the coil 23 which action will have the same effect loads being imposed upon the motor 10 the a regulator setting will be changed in response to the loads so as to permit the motor to slow down, which of course will relieve the motor of excessive loads. The efiect of the coil 51 upon the regulatormay be suitably adjusted by means'of a rheostat 52'which is inserted in the energizing circuit of the coil.

' In 0 'eration, the regulator will be adjusted y means of the rheostats 42 and 43 so as to maintain the desired substantially constant speed ratio between the electric motor 10 and the steam engine 18. Assuming that the load imposed upon the prime mover 18 is constant and that upon the motor 10 is likewise constant, then the motor will be caused to follow any changes in the speed of the I imposed upon the motor 10 increase, the setting of the regulator 20 will be changed by operationof the coil 51 so as to tend to cause the motor to slow down. \Vhen the load is again reduced, the original setting of the regulator will be restored so that it will maintain the desired speed ratio. Thus, the regulator setting willbe adjusted both during the starting operation and during the normal operation of the mill to relieve the edging roll motor of excessive overloads.

While I have described my invention as embodied in concrete form and as operating in a specific manner in accordance with the provisions of the patent statutes, it should be understood that I do not limit my invention thereto since various modifications thereof will suggest themselves to those skilled in the art Without departing from the spirit of my invention the scopeof which is set forth in the annexed claims.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A control system for a plurality of devices arranged for simultaneous operation ona length of material comprising separate operating means for each device, and means arranged to regulate the speed of one of said operating means soas' to maintain a substantially constant speed ratio between saidseparate operating means, said means being further arranged to control said regulated operating means in accordance with the load imposed thereon so as to limit the maximum value of said load.

2. A control system for a plurality of devices arranged for simultaneous operation on a length of material comprising separate operating means for each device, one of said operating means comprising an electric motor, and means arranged to regulate the speed of said electric motor so as to maintain a substantially constant speed ratio between said separate operating means and said motor, and to control said motor in accordance with the load imposed thereon so as to limit the maximum value of said load.

A control system for a plurality of demotorfor operating onedevice, and means dependent upon the speed at which said material is fed by said other device and upon the speed of said motor'for controlling said motor so as to maintain a substantially constant ratio in the speeds of said material and said motor, said means being further dependent upon the load imposed upon said motor for limiting the maximum load value imposed on said motor to a predetermined value.

4. A control system for a plurality of devices arranged for simultaneous operation on a' length of material comprising means for operating one device, an electric motor for operating another device, and means electrically responsive to the speeds of said operating means and said motor arranged to control said motor to automatically maintain a substantially constant predetermined speed ratio between said operating means andsaid motor, said means being further electrically responsive to the armature current of said motor for limiting the load value imposed on said motor.

5. In a rolling-mill installation, devices arranged for simultaneous operation on a length of material, means for operating one of said devices, an electric motor for operating the other of said devices, and a regulator for said electric motor electrically responsive to the speed at which said material is fed through the mill and to the speed of said electric motor for maintaining a substantially constant predetermined ratio in the speeds of said bar material and said electric motor, said regulator being electrically responsive to the load imposed on said electric motor whereby its setting is changed.

6. In a rolling mill installation, devices arranged for simultaneous operation on a length of material, means for operating one of said devices, an electric motor for operating the other of said devices, a regulator for said motor responsive to the speeds of saidmotor for operating another device, and

means arranged to control the speed of said electric motor so asto maintain a substantially constant ratio in the operating speeds of said prime mover and said motor, and to control said motor in accordance with the is; I

load imposed thereon so as to limit the maximum value of said load.

8. In a rolling mill installation, devices arranged for simultaneous operation on a length of material, a prime mover for operating one of said devices, an electric motor for operating the other of said devices, and

a regulator for said motor responsive to the speeds of said prime mover and said motor arranged to maintain a substantially constant ratio in the operating speeds of said prime mover and said motor, said regulator being further responsive to an electrical condition of said motor whereby its setting is varied.

9. A control system for a plurality of de vices arranged for simultaneous operation on a length of material comprising means for operating one of said devices, an electric motor for operating the other of said devices, an electric generator driven at a speed proportional to the speed of said first operated device, an electric generator driven at a speed proportional to the speed of said motor, and means jointly responsive to the voltages of said generators arranged to control the speed of said motor so as to maintain a substantially constant ratio in the operating speeds of said first operated device and said motor, 7. said means being further responsive to the load imposed upon said motor for automati- 1call limiting the maximum value of said 10. In a rolling mill installation, devices arranged for simultaneous operation on a length of material, an electric motor for operating one of said devices, an electric generator driven at a speed proportional to the speed at which the material is fed through the mill, an electric generator driven at a speed porportional to the speed of said motor, and means jointly responsive to the voltages of said generators arranged to control the speed of said motor so as to maintain a substantially constant ratio in the speeds of said material and said motor, said means being further responsive to the load imposed upon said motor for limiting the value of said load.

11. In a rolling mill installation, devices arranged for simultaneous operation on a length of material, a meansv for operating one of said devices, an electric motor for operating the other of said devices, an electric generator driven at a speed proportional to the speed of said operating means, an electric generator driven at a speed proportional to the speed of said motor, a regulator for said motor jointly responsive to the voltages of said generators for maintaining a substanof said operating means and said motor, said regulator being further responsive to the load imposed upon said motor for changing the on setting of said regulator, and means for vary- 1ingd the response of said regulator to said 12. In a rolling mill installation, devices arranged for simultaneous operation on a length of material, a means for operating one of said devices, an electric motor for driving the other; of said devices, an electric generator driven at a speed proportional to the speed of said operating means, an electric generator driven at a speed pro ortional to the speed of said motor, and a vi ratory regulator for controlling the field strength of said motor so as to re ulate the speed thereof, said vibratory regulator comprising a pair of opposed operating coils, one of said operating coils being responsive to the voltage of one of said generators and the other of said operating coils being responsive to the voltage of the other of said generators whereby a substantiall constant ratio in the operating speeds or said operating means and said motor is maintained, said regulator further comprising a third operating coil responsive to the load imposed upon said motor whereby the setting of said re lator is varied with fluctuations in said oad, and means for adjusting the setting of said regulator at will. I

13. In a rolling mill installation, devices arranged for simultaneous operation on a 95 length of material, a means for operating one of said devices, an electric motor for operating the other of said devices,'a counter-electromotive force machine arranged to regulate the field strength of said electric motor 00 whereby the speed of said electric motor is controlled, and means jointly responsive to the speeds of said operating means and said electric motor arranged to control said counter-electromotive force machine whereby a 105 substantially constant ratio in the operating speeds of said operating means and said electric motor is maintained, said means being further responsive to the load imposed upon said operating motor whereb value of said load is limite mined value.

In witness whereof, I have hereunto set my hand this 21st day of June, 1928.

LEGNID A. UMANSKY.

the maximum 110 to a predetertially constant ratio in the operating speeds

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