US 2414572 A
Description (OCR text may contain errors)
Jab. 21, 19471 JQVON DER HEIDE 2,414,572
CALENDER REEL DRIVE Filed March 20, 1944 ElmerJ. van der Heide INVENTQR.
Patented Jan. 21, 1947 arisen 2,414,572 CALENDER REEL DRIVE Elmer (i. von der Heide, Akron, omo, asslgnor, by mesne assignments, ,to Adamson United Company, Akron, Ohio, a corporation of @hio Application March 20, 1944, Serial No. 527,314 2 Claims. (or. 91-48) This invention relates to reel drives for rubber calenders and the like.
Rubber calenders commonly involve a vertical stack of three or more continuously driven accurately spaced parallelrolls for converting rubber stock into a continuous sheet of desired uniform thickness. The stock is ordinarily supplied to and between the. upper rolls of the stack and, after passing around and back and forth between successive rolls, it passes in sheet form from the bottom rolls of the stack and onto, a reel upon which it is wound.
A calender is ordinarily driven by a variable speed motor so as to permit operation at any selected speed best suited for the work at hand. Also the several rolls of thestack are ordinarily geared together to rotate at the same or at different speeds In a three-roll calender, for instance,
, the motor is usually connected to drive the center roll ofthe stack; and two separate gear trains are provided selectively operable to drive the other rolls at the same speed as the center roll or at a lower speed. In any event, the rubber sheet issues from the calender at a rate corresponding to the peripheral speed of the bottom roll of the stack, a rate that is dependent not only upon the selected speed'oi the motor but also upon the selected gear train,
The calender also commonly serves to apply to or impregnate with the rubber sheet a preformed web or backing of fabric or the like by causing the latter to pass with the sheet between the botiormed web is ordinarily received from a supply reel and the resultant composite web passes onto the receiving reel. Also, quite frequently a web of appropriate liner material from another supply reel is fed directly into the roll of material on the receiving roll to separate the convolutions thereof in a manner to prevent adhesion therebetween.
the gear trains, because of their necessary size and arrangement impose an objectionable overhung load on the calender roll and also present, a lubricating problem that has never been satisfactorily solved.
One object of the present invention is to eliminate the objections and difficulties above noted. This I have accomplished by providing a separate motor for each reel so controlled as to maintain the tension in the traveling web substantially constant throughout the range of variation in roll diameters.
Another object is to provide an improved and more eflicient drive for the reels oi calenders.
Another object is to provide in a calender a new and improved electric reel drive.
Another object is to provide a new and ims proved electric control system for effecting proper coordination between reel and web speeds under all conditions of operation of the calender.
Other more specific objects and advantages will appear, expressed or implied, from the following description of an illustrative embodiment oi the present invention.
In the accompanying drawing:
Figure 1 is a schematic view diagrammatically illustrating a rubber calender equipped with a reel drive embodying the present invention.
tom rolls of the stack where they combine under pressure to form a composite web. The pre- As heretofore arranged-the supply and receiv- Fig. 2 is a diagram of an electric control system employed. h
The calender selected for illustration and envplanation is of a type involving a vertical stack of three rolls l0, H, and 52, which are supported in the usual manner in a conventional vertical frame not shown.
The center roll it is driven from a variable speed motor i3-through a pinion l4 and bull wheel l5 carried by the roll.
The top and bottom rolls l0 and i2 are driven from the center roll H, either at the same speed as the latter through a train of gears I 8. I1, and i8 of equal size, or at a lower speed through a separate train of gears I9, 20, and 2!, the center gear 20 being smaller than gears l9 and 2|. In this instance the gears i9, 20, and 2| are shown releasably connected to the rollers through approprlate means such as keys 22. When so connected the top and bottom rolls operate at speeds less than the center roll. To eflect operation or all of the rolls at the same speed the keys 22 are withdrawn and transferred to the gears I8, l1, and I8 of the other train so as to render the rolls responsive to the latter.
A reel, here shown as a spindle 25, is arranged in fljqmi Qi the calender to receive and wind into a roll 26 the web 21 as it issues from between the bottom pair of rolls I I and i2.
A similar reel 28, supporting a supply roll .29 of fabric or other appropriate backing'material, is arranged behind the calender in position to deliver the backing material in the form of a web 30 to and between the lower pair'of rolls II and I2, by which it is pressed onto the rubber web,v
tion gear units 33 and 34 respectively. The motors are connected in parallel circuits 35 and 35'. both energized preferably by a single direct current electric generator 36 which is driven at a speed corresponding to the speed of the calender. The generator 36 is shown directly. coupled to'the main driving motor |3 so that its speed is always proportional particularly to the speed of the center roll I I.
As indicated in the diagram of Fig. 2, the generator 36 has a separately excited field 31 normally of constant strength, so that the voltage enerated and transmitted to the motors 3| and and consequently to the speed of the center roll II of the calender, and so that, unless otherwise regulated, both motors would operate at speeds proportional to that of the roll II and consequently proportional to the rate of travel of the web 21 when the roll I2 is geared to operate at the same speed as roll I].
However, the rate of travel of the web 21 is determined by the speed of the bottom roll 12, so that when the latter is geared to operate at a speed lower than that of roll II the speed of the inotors 3| and 32 should be correspondingly reduced. This is effected preferably by reducing the accomplished in various ways the control system shown and about to be described has proven quite satisfactory for the purpose. 4
In this instance each motor 3| and 32 has a separately excited field 40, 40' and'the control system shown includes a separate controller 0 or C for each motor automatically operable to regulate the motor field in a manner to maintain armature current constant throughout the range of speeds of each motor driven reel. It is, of course, understood that for any given web speed the power required to maintain a constant tension in the web is necessarily constant, and that this condition is satisfied by maintaining armature current constant, because, as above noted, the motor voltage derived from the generator 36 is constant for any given web speed. This is true 32 is proportional to the speed of the generator When the bottom roll I2 is geared to operate at a speed lower than the center roll II, the switch I 39 is opened and the resistance 31 is effective to reduce the strength of the generator field, and when theroll I2 is geared to operate at the same speed as the roll II, the switch 39 is closed to short circuit the resistance 38 and thereby increase the generator field to full strength. Whatever the conditions of operation, generator voltpensate for changes in the rate of travel of the motor torque in order to maintain a constant tension in the web 21. Also, as the web 39 unwraps from the supply reel 28the diameter of the supply roll 29 gradually decreases, thereby necessitating a gradual increase in speed and reduction in even though motor speed varies with variations in reel speeds, because such speed variations are accompanied by proportionate but invers variav nating current source through a circuit 42 and transformer 43.
Each thyratron tube 4| contains the usual heater filament 44 energized from a secondary winding 45 of the transformer 43 through a circuit 46, and the anodes 41 of each pair of tubes are connected preferably through protective resistors 48 to opposite ends of a second secondary winding 49 of the transformer 43 from which they are energized. Each pair of tubes also con tain the usual cathodes 50 which are both connected through one side of the circuit 46 to and through a variable resistor 6| to one side 52 of the motor field circuit 40 or 40' to excite the latter. In this instance side 52 of the field circult is connected to the moveable contact 53 of the resistor 5| and contains a second variable re sistor 54 by which the field strength may be manually regulated. The other side 55 of each motor field circuit is connected to the winding 49 at a midpoint thereof. The field 4|] and 40' of each motor is thus energized from one of the windings 49 through the pair of thyratron tubes connected therewith.
The fiow of electrical energy through the tubes however is regulated by regulating the potential on the grids 56. In this instance, the grids are energized from a third secondary winding 51 of the transformer 43 through means arranged to maintain the required out-of-phase relation between the grid and anode potentials. The means shown for this purpose includes a resistor 59 and a variable inductance 60 respectively connected to sistor 63. A capacitator connected across the grid 56 and cathode 50 of each tube serves to smooth out the pulsations in current flowing through the latter.
Grid regulation is effected through a control circuit between the grid and cathode of each tube and including resistors 59 and 55 connected in series with each other and with and between the variable resistor 5i and the winding 62 at a mid point of the latter. This control circuit is rendered, responsive to variations in current in the associated motor circuit 35 or 35', and for this purpose the resistor 65 is connected across the commutating field 55 or 66 of the associated ture current tends to increase, but the controller responds by progressively decreasing the field strength, and thereby maintaining constant curmotor through leads 61 and 58, so that any varia- For example, the controller C for the wind-up motor 3| may be adjusted, by adjusting the resistor 51, to provide excitation of the motor field 40 corresponding to a speed above the weak field speed of the motor, so that the motor tends to drive the receiving reel 25 at a speed greater than the calender roll. Then, when the first wrap of the web 21 is taken by the reel 25; any slack in the web is rapidly taken up and tension is established. Thereupon, the armature current immediately increases as a result of the reduction in motor speed, and the controller immediately functions to increase the field strength and thereby establish the armature current at the desired value, this value being determined not only by the setting of the resistor 5| but also by manual adjustment of the resistor 54.
rent, until maximum speed at weak field is established, a speed that corresponds to the speed of the supply reel at minimum roll diameter.
It will thus be noted that, controlled in the manner above described, both motors 3| and 32 will operate at the varying speeds and torques necessary to maintain a constant tension in both webs 2'! and at a given calenderspeed, and that this condition prevails at all speeds of operation of the calender since the voltage developed by the generator and transmitted to both motors is always proportional to the rate of operation of the calender.
Moreover, this condition maintains whether the calender is adjusted to eflect operation of the bottom roll 12 at the same speed as the center roll II or at a lower speed. Whenever the bottom roll I2 is operating at the lower speed,
the switch 39 is opened so that the resistor 38 is effective to reduce the strength of the generator field 31 and thereby reduce the voltage to a value corresponding to the lower web speed resulting from the reduced speed of the bottom roll l2; and whenever the bottom roll I2 is operating I at the same speed as the center roll I l, the switch strength so that the generated voltage is in- Thereafter, as the roll 28 on the reel 25 builds I up, the armature current tends to increase as the motor speed decreases, but to each increment of increase in current the controller responds by.
. gradually increases until full field or base speed is established, the base speed corresponding to the speed of the reel at maximum roll'diameter.
The controller C for the unwind motor 32 is 1 adjusted in a similar manner to provide an initial field strength greater than full field at base speed, so that the motor 32 tends to operate in the same direction as motor 3| but at a speed such that the speed of the supply roll 29 is less than that ofv the calender rolls. Consequently, when the web 30 is threaded into the calender, any slack therein is rapidly taken up by the calender until tension in the web is established. Thereupon, the speed of the motor 32 increases and thereafter the motor functions as a braking generator returning electrical energy to the system through the circuit 35'; The controller C iunctions-in substantially the same manner as the controller C to maintain the generated current substantially constant by decreasing the field strength as the speed of the braking generator (motor 32) increases. That is to say, as the size of the roll 23 gradually decreases with a resultant increase in braking generator speed, the armacreased to a value corresponding to the higher web speed. I
It will be further noted that with the motors 3| and 32 thus separately controlled in a man- 'ner to maintain the armature current in each circuit 35 and 35' substantially constant, the current thus maintained constitutes a measure of the tension maintained in each web 21 and 30. This is readily demonstrated. The power required to maintain a given tension in either web is the product of web speed times web tension, and the power supplied by each motor for maintaining that tension is equal to the product of the voltage and current maintained in each motor circuit, and since, as above pointed out, the voltage in both circuits 35 and 35' is the same for any given web speed, it necessarily follows that the current maintained in each circuit 35 and 35 is proportional to the tension in \the corresponding web. Therefore, an ammeter placed in either circuit 35 or 35' will provide an accurate visible indication of the tension in the web 21 or 30, respectively, and constitute a useful guide in regulating the tension in either web which may be readily accomplished by appropriate manual adjustment of one or the other of the variable resistors 54.
A reversing switch 10 is preferably included in the field circuit 52-55 of each motor 3| and 32 to permit reversal of either motor at will.
Various changes may be made in the embodiment or the invention hereinabove specifically described without departing from or sacrificing the advantages of the invention as defined in the appended claims.
I claim: 1. The combination of a calender having a stack of rolls coacting to form and apply a-sheet sequent variation in the rate oi discharge of said combined web and sheetfrom said rolls, a second motor for driving said reel, a generator driven by said first named motor for normally maintaining the armature voltage of said second motor proportional to the speed of said first named motor, means for varying the field strength of said generator to thereby modify said voltage in accordance with the variation in speed ratio between said rolls, and an electronic controller responsive to the armature current of said second motor for maintaining said armatur current substantially constant throughout the speed 1 range of said reel.
2. The combination 01' a calender having a stack of rolls coacting to form andapply a sheet or rubber or the like to a web, means for supplying the web thereto, a reel for receiving the'combined web and sheet formed by said rolls, a motor for driving said reel at varying speeds tocompensate for variations in diameter of the roll of material thereon, means adjustable to vary the speed ratio between said rolls with a consequent variation in .the rate of discharge of said combined web and sheet from said rolls-means for maintaining the armature voltage of said motor substantially proportional to said rate of discharge of said combined web and sheet. and an electronic controller responsive to the armature current of said motor for maintaining. said current substantially constant.
ELMER J. VON DER HEIDE.