US2427771A

US2427771A - Control of electrolytic processes

Info

Publication number: US2427771A
Application number: US468217A
Authority: US
Inventors: John R Erbe
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1942-12-08
Filing date: 1942-12-08
Publication date: 1947-09-23
Anticipated expiration: 1964-09-23

Description

Sept. 23, 1947. J. R. ERBE CONTROL OF ELECTROLYTIC PROCESSES Filed Dec. 8, 1942 m M 9 Z a 0 F m a INVENTOR (fa/7n K, Erfie, L 61 ATTO EY WITNESSES: M/ I %z?@ Wm Patented Sept. 23, 1947 2,427,771 CONTROL OF ELECTROLYTIC PROCESSES John R. Erbc, Pittsburgh 16, Pa.., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application December 8, 1942, Serial No. 468,217

The present invention relates, generally, to the control of electrolytic processes, and, more particularly, to the control of the electrolytic treatment of continuously moving lengths of material.

In the manufacture of metal coated or plated materials such as tin-plate, it has been the practice to apply the coating material to the material to be coated by dipping it into the molten coating material. It has been found that this process is wasteful of the coating material for the reason that it is very difiicult to control the thickness of the coating and, as a consequence, much more of the coating material is used than is necessary to properly coat the material for the purpose for which it is to be used.

It has been found that such'metal coatings may be applied very uniformly by electrolytic means, and long sheets of material have been thus coated by passing them through an electrolytic bath. The amount of material deposited electrolytically is a function of the length of time the material to be coated is exposed to the plating current and the density of the plating current. It will be apparent, then, that a uniform deposit of coating material will be made upon a strip of material as it moves at a constant speed through an electrolytic bath and the current density is kept constant.

In order to expedite the production of plated material by this electrolytic process, it has been proposed that the process be made continuous by securing the ends of successive lengths of'material together as they are fed to the plating apparatus to thereby avoid stopping the length of material and the plating apparatus for the purpose of threading each new length of material through the plating apparatus. In the operation of such a continuous plating system it is necessary that the speed of travel of the length of material through the plating apparatus be decreased materially When the next succeeding length of material is to be attached thereto to form the continuous length of material. It will be apparent that this decrease of the speed of the length of material through the plating bath will cause the length of material to be acted upon by the plating current for a greater period of time than when it is traveling at normal speed and it will be necessary to decrease the density of the plating current to prevent the deposition of an excess quantity of coating material.

An object of the present invention is to provide a control system for a continuous electrolytic process which shall function to coordinate the speed and current density in the process.

Another object of the invention is to provide a. control system for an electrolytic process for continuously treating a continuously moving length of material which shall function to so 7 Claims. (Cl. 204-211) coordinate the current density and the speed of travel of the length of material as to produce uniform treatment of the length of material regardless of changes in the speed of travel of the length of material.

A further object of the invention is to provide a control system for an electrolytic plating process for plating a continuously moving length of material which shall function to so coordinate the speed of travel of the length of material and the plating current density as to produce a uniform plate thickness regardless of changes in the speed of travel of the length of material through the electrolyte.

These and other objects and advantages of the invention will be apparentv from the following detailed description taken in connection with the accompanying drawing the single figure of which is a diagrammatic representation of an electrolytic plating system embodying the principal features of a preferred embodiment of the invention.

Referring to the drawing, a strip of material 2 is drawn through an electrolyte 4 in a tank 6 by means of a motor 8 which drives roll members I0 and I2 Which in turn engage the strip 2. The armature of the motor 8 is connected to be energized by a generator [4 whose output potential may be varied by a rheostat l6 which varies the energization of its field winding Hi. The generator [4 may be driven by any suitable means such as a substantially constant speed alternating current motor 20.

A plurality of plating generators, such as generators 22 and 24, may be driven by the motor 20 and connected by means of

conductors

26 and 28 to separate sets of plating electrodes 30 and 32. The other terminals of the generators 22 and 24 are connected by means of a common conductor 34 to contact

rolls

36 and 38 which engage the strip 2 as it passes through the electrolyte.

Pilot generators

40 and 42 are connected to be driven by the motor 8 and their speeds are, therefore, proportional to the speed of travel of the strip 2 through the electrolyte 4.

Generators

44 and 46 may be continuously driven by any suitable means such as a substantially constant speed alternating current motor 48. The

generators

40 and 46 are connected in series circuit relation as shown to energize the field windings 50 and 52 of the plating generators 22 and 24, respectively, through variable resistors 54 and 56, respectively.

The generator 44 has a field Winding 58 which is energized through a variable resistor 60 by the potential drop across a shunt device 62 in the common conductor 34 of the platirig current circuit. The excitation of the generator 44 thus varies in ccordance with the plating current and its output potential is, therefore, a measure of the plating current density. A regulator 54 functions to control a variable resistor 65 which is connected in series circuit with a variable resistor 65 and the field winding 68 of the generator 46 so that the output potential of the generator 46 is varied in accordance with the setting of the variable resistor 65 by the regulator 64.

The regulator 64 comprises a reversible motor l5 which is connected in driving relation with the variable resistor 65 and which may be made to rotate in a reverse or forward direction by means of a movable contact element 12 in co operation with

fixed contact elements

14 and 16. The movable contact element 12 is mounted upon a pivoted arm 13 which is disposed to be operated in opposite directions by solenoids l8 and 80.

The solenoid 18 is connected as shown to be energized by the pilot generator 42 and thus acts upon the pivoted arm 13 with a force proportional to the speed of the strip 2 through the electrolyte 4. The solenoid 80 is connected to be energized by the output potential of the generator 44 and, therefore, acts upon the pivoted arm 13 with a force which is proportional to the density of the plating current.

In the operation of the system, since the output potential of the pilot generator 40 is proportional to the speed of the strip 2 through the electrolyte 4, the excitation of the plating generators 22 and 24 will vary in accordance with the speed of the strip 2, and, since the plating current varies in accordance with the output potential of the plating generators 22 and 24, the plating current will also vary in accordance with the speed of the strip 2. The variable resistor 60 may function as a calibrating resistor to fix the desired ratio or proportionality between the speed of the strip 2 and the plating current. If there is any variation in the proportionality between the speed of the strip 2 and the plating current, the resulting unbalance of the forces acting on the pivoted arm 13 will cause the contact element F2 to engage one of the fixed contact elements M and '16 which in turn will cause the motor to operate the variation resistor 65 in such a direction as to cause the generator 45 to add to or subtract from the excitation of the generators 22 and 24 to thereby compensate for the variation in the proportionality between the speed of the strip 2 and the plating current.

In order to obtain the best plating results it may be desirable that the plating current provided by one of the generators 22 and 24 be greater than the other. The variable resistors 54 and 56 are provided to so proportion the excitations of the plating generators 22 and 24 as to produce any desired proportionality between the plating currents provided by these generators.

When it is desired to reduce the speed of the strip 2 to such a speed as Will permit the attachment of the leading end of a succeeding strip of material to the following end of the strip to thereby provide a continuous process and continuous movement of the strip 2, the speed of the strip 2 may be reduced by reducing the excitation of the generator M by means of the variable resistor 16. When the speed of the strip 2 is thus reduced, the output potential of the generator 46 will be reduced proportionally which in turn will cause a proportionate reduction of the excitation of and, therefore, the plating current provided by the plating generators 22 and 24. The regulator 64 will function in response to the speed of the strip 2 and the plating current density to compensate for any variations in the proportionality of the speed of the strip 2 nd plating current. Thus the desired amount of coating material which is to be deposited on the strip 2 will be substantially the same regardless of variations in the speed of the strip 2.

It is to be understood that the regulator 64 is merely illustrative of one type of regulator that may be employed to perform the regulator function described herein, and that any regulator that will function in response to potentials proportional to the speed of the strip and the plating current may be employed.

It is also to be understood that only two plating generators have been shown and described herein merely for the purpose of illustration and that as many plating generators as desired may be employed and controlled in accordance with the principles described herein.

It is also to be understood that the description of the electrolytic process as an electroplating process is merely illustrative of the principles of operation of the control system and that the control system may be employed if desired in any electrolytic process in which it is desired that a current density in the electrolytic process vary in any desired manner in response to variations in the speed of the length of material which is being electrolytically treated in the process.

Thus it will be seen that I have provided a control system for an electrolytic plating process for plating a continuously moving length of material which shall function to so coordinate the speed of travel of the length of the material and the current plating density as to produce uniform plate thickness regardless of the speed of travel of the length of the material through the electrolyte.

In compliance with the requirements of the patent statutes, I have shown and described herein a preferred embodiment of my invention. It is to be understood, however, that the invention is not limited to the precise construction shown and described but is capable of modification by one skilled in the art, the embodiment herein shown being merely illustrative of the principles of my invention.

I claim as my invention:

1. In a control system for an electrolytic process, generator means for supplying current to the electrolytic process, an exciter for said generator means, means for varying the excitation of said generator means in accordance with the speed of travel of a length of material through the electrolytic process, and means for varying the ex citation of the exciter means in accordance with the variation of the proportionality between the speed of the length of material and the current supplied to the electrolytic process.

2. In a control system for an electrolytic process, generator means for supplying current to the electrolytic process, exciter means for varying the excitation of the generator means, means responsive to the speed of travel of a length of material through the electrolytic process for varying the excitation of said generator means, and regulator means responsive to the variation of the proportionality between the speed of the length of material and the current supplied to the electrolytic process for controlling said exciter means for further varying the excitation of said generator means independently of said speed responsive means.

3. In a control system for an electrolytic process employing an electrolytic bath through which a length of material is moved, main generator means for supplying current to the electrolytic process, a pilot generator, means for driving the pilot generator at a speed proportional to the speed of travel of a length of material through the bath, an auxiliary generator, means connecting said pilot generator and said auxiliary generator in series circuit relation to excite said main generator means, and means including regulator means jointly responsive to the variations of the proportionality between the speed of the length of material and the current supplied t the electrolytic process for varying the excitation of the auxiliary generator, whereby said pilot generator and auxiliary generator cooperate to so control the excitation of the main generator means as to maintain a predetermined ratio between the speed of the material and the current supplied to the bath regardless of the speed of the material.

4. In a control system for an electrolytic process wherein a length of material is moved through the process, main generator means for supplying current to the process, a first pilot generator operable to develop an output potential proportional to the speed of the moving material, an auxiliary generator, circuit means connecting said first pilot enerator and said auxiliary generator in series circuit relation to the excitation circuit of the main generator means, said first pilot exciter functioning to vary the excitation of the main generator means in accordance with the speed of the moving material, a second pilot generator operable to develop an output potential proportional to the speed of said material, a third pilot generator operable to develop an output potential proportional to the current supplied to the process by the main generator means, and regulator means jointly responsive to the output potentials of said second and third pilot generators for controlling the output potential of the auxiliary generator thereby to maintain a predetermined ratio between the speed of the moving material and the current supplied to the process.

5. In a control system for an electrolytic process wherein a length of material is moved through the process, main generator means for supplying current to the process, a first pilot generator operable to develop an output potential proportional to the speed of the moving material, an auxiliary generator, circuit means connecting said first pilot generator and said auxiliary generator in series circuit relation to the excitation circuit of the main generator means, said first pilot exciter functioning to vary the excitation of the main generator means in accordance with the speed of the moving material, a second pilot generator operable to develop an output potential proportional to the speed of said material, a third pilot generator operable to develop an output potential proportional to the current supplied to the process by the main generator means, a motor-operated rheostat for controlling the excitation of the auxiliary generator, and a differential relay jointly responsive to the output potentials of said second and third pilot generators for controlling the operation of the motor-operated rheostat, thereby to maintain a predetermined ratio between the speed of the moving material and the current supplied to the process.

6. In a control system for an electrolytic process wherein a length of material is moved through an electrolytic bath, a main generator for supwhereby the pilot generator and regulator means function together to so control the output current of the main generator as to maintain a predetermined ratio between the speed of travel of the material through the bath and the current supplied to the bath regardless of the speed, and means operable to control the regulator means to vary said regulator means to vary said ratio of speed and current.

7. In a control system for an electrolytic process wherein a length of material is moved through an electrolytic bath, a main generator for supplying variable amounts of current to the bath, said generator having a field excitation winding, a variable voltage exciter for the main generator, a first pilot generator operable to develop an output voltage proportional to the speed of movement of the material through the bath, circuit means connecting the exciter and said pilot generator in series circuit relation with the field excitation winding of the main generator, whereby the current supplied to the bath is roughly proportional to the speed of the material, a second pilot generator operable to develop an output voltage proportional to the speed of movement of the material, a third pilot generator operable to develop an output voltage proportional to the current supplied to the bath by the main generator, regulator means jointly responsive to the output voltages of the second and third pilot generators operable to control the excitation of the variable voltage exciter thereby to cause the ariable voltage exciter to cooperate with said first pilot generator in the control of the output current of the main generator to maintain a predetermined proportionality between the speed of the moving material and the current supplied to the bath regardless of the speed at which the material is moved through the bath, and means operable to vary the voltage output of the said third pilot generator independently of the current output of the main generator to cause the regulator to maintain any desired ratio of speed and'current.

JOHN R. ERBE.

REFERENCES CITED The following references are of record in the