US3417008A - Switch for electrochemical processes - Google Patents

Description

De@ 17, 1958 M. A. KouruNlAK SWITCH FOR ELECTROCHEMICAL PROCESSES Filed Jan. 15, 1965 9% p r faxus/4'.

3,417,008 SWITCH FOR ELECTROCHEMICAL PROCESSES Michael A. Koltuniak, Warren, Mich., assignor to The Udylite Corporation, Warren, Mich., a corporation of Delaware Filed Jan. 15, 1965, Ser. No. 425,905 17 Claims. (Cl. 204-225) ABSTRACT F THE DISCLOSURE A switch assembly in an electroplating processing system to selectively, through operation of a slidably movable contact, perfor-m switching functions for electroplatmg voltages.

This invention relates generally, to a switch for use in electroplating machines, and more particularly to an electrical switch for use in electroplating operations requiring different levels of electrical energy at various stages of the operation.

In electroplating machines of various types including those for chrome electroplating, the articles to be plated are normally transported into position over the plating tanks by means of horizontally disposed track members. The individual articles are supported on a vertically movable cathode rail mem-ber which is supported on a shoe mem-ber and the articles are lifted into and out of the tank by supplying mechanical power thereto. The shoe member is adapted to slidably engage a vertical Ibar which is electrically connected to a source of electrical energy supply. Thus electrical energy issupplied to the workpieces as they are being lowered into the electroplating bath and United States Patent O moved therealong in a horizontal direction through the processes performed by the electroplating bath.

In supplying electrical energy to the complete electrochemical system, it has been the practice to supply each of the entry or prestrike, strike and plating voltages with individual power supplies. Thus, in a typical situation, a rectifier which has been adjusted for two to four volts output is connected to supply the entry voltage, a twelve volt preset rectifier to supply the strike voltage and a seven volt preset rectifier to supply the normal plating voltage. With the inherent high cost of each of the above mentioned rectifiers, it is desirable Vto eliminate any duplication of rectifiers or utilize a single rectifier for a plurality of functions where possible. However, to merely regulate the output of a single rectifier to provide a plurality of outputs creates certain control problems in electromagnetically controlled supplies which are peculiar to the electrochemical processes art. One of these problems lies in the fact that the output terminals are open circuited prior to the entry of the work into the bath.

The power supplies being used for supplying the entry voltage to the workpieces comprise a normal commercial source which is connected to a saturable reactor type of control means and thence, through output transformer, is connected to the load members. When the load is out of the electroplating bath the output terminals of the entry rectifier are open-circuited thus drawing no load current from the output transformer. Accordingly, the high impedance of the primary windings of the reactor and output transformer preclude the current drawn through the reactor power windings to be of sufiicient value to provide a magnetizing current which will enable the operator to control the voltage available to the load terminals prior to the entry of the workpieces into the bath. In the normal type of saturable reactor control, a magnetizing current of at least 10 percent of the full load current is needed to control the output voltage at no-load current.

In this situation, the load pieces enter the electroplating bath at the full voltage level of the rectifier, this voltage 3,417,00 Patented Dec. 17, 1968 Fice being higher than that which is normally desired. As the work is lowered into the bath and prior to drawing a full load current for the entry voltage (prior to achieving control of the rectifier) a high voltage as compared to the submerged area exists in the tips of the work resulting in a burning of the tips as they are immersed. This condition exists until sufiicient work area has been immersed into the electroplating bath to draw sufiicient current through the load terminals thus enabling the saturable reactor to gain control of the load voltage. The same situation exists as the workpieces are being withdrawn from the bath on completion of the electroplating operations thereon, that is, the last portion of the work to be withdrawn will draw an extremely large current per unit area.

`Certain other prior art supplies have been provided with a fixed dummy load resistor `which draws suflicient magnetizing current through the saturable reactor to enable the reactor to control the output voltage prior to the entry of the workpiece into the bath. However, this system has certain inherent deficiencies in that a fixed load resistor will not provide the proper output characteristics for all levels of output Voltage and current. Thus, it is necessary that the load resistor be made variable in order to provide a capability of varying the output characteristics in accordance with the desired load. Also, to permanently connect a dummy resistor across the load terminals has the inherent defect of drawing power from the power supply and dissipating it in a non-usable manner when this current should be drawn through the load and required to perform the desired -work functions. Accordingly, it has been found that it is undesirable to provide a fixed load resistor across the output terminals of the reactor where various levels of output voltage and current exist.

In a unit constructed according to the principles of the present invention, a single reactor is provided to supply the voltage for the entry of the workpieces into the bath, the strike voltage and the normal plating voltage. In order to accomplish this result with a single rectifier, it has been. found that a load resistor may `be connected across the output terminals for that period of the process wherein the workpieces are lowered into the lwork bath and prior to the impressing of the strike voltage across the workpieces. Thus in a unit constructed according to the principles of the present invention, a switch is provided which connects a dummy load resistor linto the circuit only during the period wherein the load is -being lowered into the work bath and, when the load is fully lowered in the work bath, the load resistor is disconnected from the reactor supply and the strike voltage is impressed across the workpiece terminals.

Accordingly, it is one object of the present invention to provide an improved electrical system for use in electrochemical processes.

It is another object of the present invention to provide an improved method and apparatus for supplying a plurality of voltages to a workpiece from a single rectifier.

It is another object of the present invention to provide an improvedv switching assembly for use in conjunction with a power supply for an electrochemical process.

It is still another object of the present invention to provide an improved switch assembly which is capable of enabling the power supply to control the output voltage prior to the entry of the workpieces into a -bath of an electrochemical process.

lt is stillvanother object of the present invention to provide an improved switch assembly for use in electrochemical processes wherein certain interconnections between portions of the switch assembly are made inflexible and long lasting.

1t 'is still a further object of the present invention to provide an improved switch assembly for use in electrochemical processes which may be easily applied to existing systems.

It is still a further object of the present invention to provide an improved switch assembly for use in electrochemical processes which is simple to construct and inexpensive to manufacture.

Further objects, features, and advantages of this invention will become apparent from a consideration of the following description, the appended claims and the accompanying drawing in which;

FIGURE 1 is a representative illustration of a typical chrome plating system utilizing a single rectifier to provide the entry voltage, the strike voltage and a preliminary plating voltage. Also a separate rectifier is utilized to supply the main plating voltage, in accordance with certain principles of the present invention;

FIG. 2 is a schematic diagram of the system of FIG. l, and particularly illustrating the details of one preferred embodiment of the switch assembly of the present invention;

FIG. 3 is a side view partially in cross section of another embodiment of a switch assembly of the present invention; and

FIG. 4 is a schematic diagram of the electrical circuitry power supply which may be utilized in conjunction with the electrochemical process system of FIG. 1 wherein the preliminary voltages of the process are supplied by a single rectifier.

Referring now to FIG. l of the drawing, there is illustrated an electrochemical process system 10, which generally comprises a plurality of plating tanks 12, 14 and 16 which are filled with a chemical solution 18, such as would be used in a chrome plating process, wherein t-he system is supplied with electrical energy from a rectifier 20. The positive or anode voltage is fed from terminal 22 of the rectifier 2t) to a plurality of anode rods 24 by means of an anode bus bar 26 which is suitably electrically connected thereto. The anode rods are adapted to be supported in a hook-type end portion 30 of the anode bus bar 26, and it is to be noted that t-he rectifier may be interconnected with a plurality of anode bus bars similar to 26 to supply a positive potential to each of the tanks 12, 14 and 16. A plurality of workpieces 32 are adapted to be suspended from a plurality of cathode rods 31 in a well known manner, with the workpieces 32 being lowered into position by means of a vertically slidable cathode shoe 36.

The anode voltage is supplied from the positive terminal 22 of the rectifier to the anode rail 24 by means of a fixed bus bar 26 connected thereto in a conventional manner. The cathode voltage for both the entry and strike voltages are supplied from a negative terminal 38 to a Vertical cathode rail 40 by means of fixed bus bar 42. It is to be noted that the rail 40 comprises two sections, a lower section 44 having an upward curve at one end thereof and an upper section 46, the two sections being separated by suitable electrically insulating material 48. Thus the cathode voltage is supplied from terminal 38 through bus bar 42 to lower section 44. The voltage is then supplied to the upper portion 46 by means of a conductor 50 through vertically slidable shoe 36. In this way the negative cathode voltage is supplied to both the lower 44 and upper 46 portions of the cathode bar 40. With the slidable shoe 36 in the raised position, as illustrated in FIG. l, the circuit between terminals 22 and 38 of rectifier 20 is seen to be open circuited insofar as the workpiece is concerned, thereby precluding any current flowing therebetween. As was stated above, with zero current flowing in the output circuit, the rectifier cannot be controlled to lower the output voltage to the desired lentry voltage. Thus, the voltage available at 22 and 38 and accordingly at cathode bus 4G and anode bus 26 will be the full rated rectifier voltage.

In order to alleviate the problems recited above, the upper portion 46 of the cathode bus bar 40 is interconnected with the positive terminal 22 of the rectifier supply 20 by means of a bus bar 52 having a resistor 54 disposed between one end of the bus bar 52 and the terminal 22. Thus, as the cathode shoe 36 is in its fully raised position and until such time as it leavestthe lower edge of the section 46, the resistor 54 will be connected in the load circuit in series with the output terminals of the rectifier 20 thereby providing a load circuit for the flow of current. In this manner, the necessary magnetizing current to achieve control of the saturable reactor will be provided and the voltage of the rectifier 20 may be lowered to the necessary two to three volt entry voltage.

The shoe 36 is formed wit-h a generally vertically disposed portion 58 having a vertical flat surface thereon which is in intimate electrical contact with the vertical surface of upper portion 46 to provide a sliding contact between the vertical portion of bar 40 and the shoe 36. Thus, as the shoe 36 leaves the upper portion 46 and passes from the insulating portion 48 to the lower portion 44, the resistance 54 is disconnected from the load circuit, thereby providing the full controlled voltage to the anode and cathode terminals in lieu of having a portion of that voltage dropped across resistor 54. However, it is to be noted that when the shoe leaves portion 36 and engages portion 44 the workpiece 32 is fully immersed and the desired voltage may be applied without the danger of burning the work. As was stated above, the voltage applied at the downmost position of the shoe 36 is the strike voltage which is required to properly plate the crevices and other indented portions of the workpiece, as is well known in the art. This Vstrike voltage may be applied at such time as the cathode rail 31 strikes a limit switch 60, or any type of switching apparatus, as will be hereinafter explained.

Referring now to FIG. 2, thereis illustrated a schematic representation of the system of FIG. l, and particularly illustrates the details of a switch assembly 62 which may be incorporated into the system described above. In this figure, the switch 62 is formed of a generally upstantling vertical portion 64 and a horizontally disposed lower portion 66, with an insulating portion 68 electrically separating the upper portion 64 from the lower portion 66. As in FIG. l, the flexible connector 50 interconnects the shoe 36 with the lower portion 66 and FIG. 2 clearly illustrates the electrical connections between the various portions of the switch and the assembly. After the workpiece 32 is lowered into the tank 14, it is positioned on a cathodic support member 70 which has been connected to a separate plating rectifier 72. With the workpiece supported on member 70, a suitable switch may be provided to energize rectifier 72 and thereby supply the plating current to the bath after a suitable time has elapsed in which the strike voltage has been applied or the plating rectifier may be continuously energized. On completion of the necessary plating operation, the workpiece is then again lifted from tank 14 and passed on to the next station wherein a further plating operation will be performed on the workpiece.

The rectifier 20 will supply the entry voltage through a circuit including the resistor 54, the strike voltage and the preliminary plating voltage. The preliminary plating voltage allows the work to be translated to the cathode 31 or 70 without a voltage differential existing between cathode 36 and cathodes 31 and 70 respectively.

As is seen in FIG. 2, when the workpiece 32 is at its uppermost position, the current flows from terminal 38 through conductor 42 to lower portion 66. The current is then directed around the insulator member 68 by means of a tiexible conductor 50 and, through shoe 36, upper member 64 and conductor 52, is led through resistor 54. The other end of resistor 54 is connected through conductor 3U to the positive terminal 22 of the rectifier 20. When the shoe 36 reaches a position wherein it is in engagement with portion 66, the resistor 54 and upper portion 64 are open circuited, thus out of the load circuit of the rectifier. The load current then flows from terminal 38, through bus 42, the lower portion 66, cathode shoe 36, workpiece 32, through the electrical bath to the positive terminal of the rectifier by means of the anodes 24. As is the case in all plating operations, the workpieces are then moved to a position on rail 70 wherein the normalA plating current is applied through plating rectifier 72 by means of a cathode bus 73.

Referring now to FIG. 3, there is illustrated an alternate form of the switch assembly described above wherein a switch 76 is formed of a generally vertical portion 78 and a generally L-shaped portion 80 which are electrically isolated from one another by means of insulating material 82 disposed therebetween. A shoe member 84 slidably engages the coplanar edge surfaces of portions 78 and 80 to electrically interconnect the portions until such time as the shoe reaches a level adjacent the horizontal portion of the L-shaped member 80. Thus, as the shoe 84 slides downwardly, both sections 78 and 80 are interconnected thereby connecting resistor 54 into the load circuit. When the shoe 84 reaches the horizontal portion, the resistor 54 is eliminated from the load circuit. It is to be noted that the liexible connector 50 described above has been eliminated and the section 80 serves a dual function, that is the function served by the fiexible conductor 5i) and the lower portion 66 which is connected to the negative terminal 38.

Referring now to FIG. 4, there is illustrated a typical circuit which may be utilized in conjunction with the plating system and switch assembly described above wherein a single rectifying unit supplies all of the preliminary voltages required for the process. The circuit has been chosen purely for illustrative purposes as illustrating one circuit arrangement which could be used in connection with the assembly described above to illustrate the switch. In the circuit, a suitable source of AC supply 90 supplies the primary winding 92 of an output transformer 94. The current through the primary winding 92 is controlled by a saturable reactor 96 having a bias winding 98 thereon as is conventional. The output of transformer 94 is supplied to output terminals 100, 102, by means of a center-tapped secondary winding 104 of transformer 92. The output is rectified by rectifying diodes 106 connected in the outer conductors in the normal full wave fashion, and the secondary winding of transformer 94 is center-tapped at 108 to provide the negative terminal. It is to be noted that the resistor 54 has been illustrated as connected between terminals 100 and 102 and switch 62 is illustrated as opening and closing the circuit to include resistor 54 in the load circuit at the proper portion of the plating cycle. It is to be understood that any of the switches described above may be used in place of switch 62.

The bias winding 98 is applied with biasing current from a low voltage transformer 112, the output of which is suitably rectified by means of a rectifying bridge 114 to give a direct current output between conductors 116 and 118. This output is fed to a plurality of variable voltage divider resistors 120, 122 and 124, all of which are connected in parallel. The voltage -divider 120 supplies the bias winding with a current which produces a voltage across terminals 100, 102 corresponding to the magnitude of the entry voltage. The voltage divider 122 provides a bias current in winding 98 which will produce an output voltage corresponding to the strike voltage and the voltage divider 124 will produce a current in winding 98 which will produce a voltage at the output corresponding to the plate voltage.

Thus for the circuit illustrated in FIG. 4, each of the voltage functions are produced by a single rectifier and the two rectiliers described in conjunction with FIGS. l and 2 supply all of the preliminary voltages and the main plating voltage, thereby eliminating additional cost. It is to be understood that a similar switching arrangement may be provided in conjunction with au exit rectifier supplying a plating and exit voltage. Thus, as a slidable shoe lifts the work from the tank, a resistor may be connected across the output terminals to provide control of the exit station rectifier as the work is being withdrawn.

The control circuitry is illustrated as having a limit switch 110, which may correspond to limit switch 60, and may be actuated by the downward movement of cathode rod member 31. As switch is closed, a timing relay TR is energized coincidentally with the energization of a relay R1. A pair of normally closed contacts RC1, controlled by relay R1, are connected in series circuit with the voltage divider and the bias winding 98 and serve to control the current flowing in conductor to either the conducting or nonconducting state. The timing relay TR controls the condition of a normally open switch TRS, and closes switch TRS at such time as the relay TR times itself out. The closing of switch TRS energizes a relay coil R2 from the common source of electrical energy. A pair of normally closed contacts RC2 and normally open contacts RC1 are in series circuit with the voltage across resistor 122 and bias winding 98 and are controlled by the energization of relays R2 and R1, respectively. In a similar fashion a pair of normally open contacts RC2, controlled by relay R2, are in series circuit with the voltage across resistor 124 and bias winding 198.

In operation, as limit switch 110 is closed due to the engagement therewith by rod 31, FIG. 1, the timing relay TR and the coil of relay R1 are energized simultaneously. It is to be noted that prior to the closing of limit switch 110, that the voltage divider 120 fiows current through the bias winding 98 through closed contacts RC1 to impress the entry voltage on the output terminals. This voltage corresponds in time to the downward travel of shoe 36 and prior to the engagement of rod 31 with the limit switch 60. On the energization of relay R1, normally closed contacts RC1 are opened and normally open contacts RC1 are closed, thereby putting current through the bias winding 98 by means of voltage across voltage divider 122. Timing relay TR then times itself out and closes a switch TRS in series circuit with the relay coil R2. Thus current fiows through relay coil R2 to open normally closed contacts RC2 and close normally open contacts RC2. In this way, the current fiowing through bias winding 98 is supplied by the voltage divider 124 and the voltage -across divider 122 is open-circuited by the opening of normally closed contacts RC2. Thus the output terminals are taken through a sequence of voltages, as for example, an entry voltage of two to four volts for the period in which the shoe 36 is in its downward travel, and then for the strike voltage of approximately twelve volts during the period when timing relay TR is timing itself out, to the plate voltage of the order of six volts for the rest of the plating cycle.

From the foregoing, it is seen that applicant has provided an electroplating system wherein lmeans is provided for controlling the voltage of a single rectifier to provide a low entry voltage thereby protecting the workpieces as they are lowered into the bath. In this Way, the necessity of plural rectifiers is removed both from the starting cycle and from the finishing cycle. Also, the syste-m includes an entry voltage, a strike voltage and a plating voltage which may be provided from a single rectifier while maintaining complete control and excellent utilization of the power available from the rectifier. As a further consideration, a switching circuit has been provided wherein the entry voltage is impressed across a dummy impedance when the output terminals are open-circuited and no-load current is flowing. This impedance is impressed across the output line of the terminals only at such time as it is needed, as in the entry voltage situation, and is eliminated from the circuit at times when the dummy resistor is not required. Thus the problem of providing a variable resistor which must be manually varied or an imperfect control of the load voltage is alleviated.

While it will be apparent that the embodiment of the invention herein disclosed is well calculated to fulfill the objects of the invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

1. In combination with an electrochemical processing apparatus having an anode electrode and a cathode electrode, one of said anode and cathode being a workpiece, a power supply having terminals for providing an anode and a cathode potential to said electrodes and means for moving said workpiece between a raised position and a lowered position, a switch assembly comprising a first conductive portion connected to one of said terminals, a second conductive portion separated from said first portion and electrically insulated therefrom, impedance means connected between said second portion and the other of said terminals, and means slidably movable and selectively engaging said first and second portions for varying the effect of said impedance from said power supply during a portion of said movement.

2. The combination of claim 1 wherein said first portion comprises a rectangular bar member and said second portion comprises an L-shaped member nesting said first portion.

3. The combination of claim 1 wherein said last named means comprises a slidable shoe selectively engaging said first portion and said second portion.

4. The combination of claim 3 wherein said shoe engages both said first and second portions when said workpiece is raised.

S. The combination of claim 2 wherein said last named means comprises a slidable shoe selectively engaging said first portion and said second portion.

6. The combination of claim 2 wherein said shoe engages both said first and second portions when said workpiece is raised.

7. An electrochemical processing system for electrochemically operating on a surface of a workpiece including a bath, said workpiece being an anode or cathode electrically connected through said bath to an electrically opposite anode or cathode immersed in said bath, means for supplying electrical energy to said anode and cathode output electrodes through output terminals connected thereto, impedance means and connecting means for selectively connecting said impedance means across said output terminals when said workpiece is in said raised position, means for moving said workpiece between said raised and lower position, said connecting means comprising a first conductive portion connected to one of said terminals, a second conductive portion rigidly supported relative to and insulated from said first conductive portion having means connected to one end of said imped ance means, and conductive means selectively in contact with said first and second conductive portions and slidably movable thereon for selectively connecting the impedance means across said terminals when said workpiece is in the raised position and disconnecting the impedance means from said terminals when said workpiece is in the lowered position.

8. The system of claim 7 wherein the conductive means is a slidable shoe engaging the rst conductive portion when the workpiece is raised and the second conductive portion when the workpiece is lowered and current conducting means connecting said shoe to said second conductive portion.

9. The system of claim 8 wherein said shoe supports the workpiece during a portion of the process.

10. The system of claim 7 wherein said second conductive portion is spaced from said first conductive portion and insulating material is disposed therebetween.

11. The system of claim 7 wherein said first conductive portion is a rectangular shaped bar member and said second conductive portion is a rectangular shaped bar member disposed spaced from said first conductive portion and having insulating material disposed therebetween.

12. The system of claim 7 wherein said first conductive portion is a rectangular shaped bar member and said second conductive portion is an L-shaped member nesting said first conductive portion therein.

13. The system of claim 12 wherein said conductive means simultaneously engages said first and second conductive portion at least when said workpiece is in the raised position.

14. A switch assembly for use in combination with a power supply for an electrochemical process having an anode and a cathode connected to said power supply comprising first means including a conductive member connected to one electrode of the power supply, second conductive means fiXedly supported relative to said first means and electrically insulated therefrom, impedance means connected to the other terminal of the power supply at one end thereof and to said second means at the other end thereof, and conductive means slidably mov able relative to said first and second means and in contact therewith for electrically connecting said impedance means across said power supply during at least a portion of said movement.

15. The switch assembly of claim 14 wherein the first means is a conductive, rectangular shaped bar member and the seco-nd means is an L-shaped conductive bar member nesting said first means.

16. The switch assembly of claim 15 wherein said conductive means is a shoe member slidably and selectively engaging said first and second means.

17. The switch assembly of claim 16 wherein said shoe member simultaneously engages both said first and second means during at least a portion of the sliding travel of said shoe.

References Cited UNITED STATES PATENTS 2,374,199 4/1945 Harris 204-228 2,457,510 12/1948 Van Ornum 204-225 2,515,192 7/1950 Chester 204-228 XR 2,849,392 8/1958 Scott 204-198 FOREIGN PATENTS 779,906 7/1957 Great Britain.

JOHN H. MACK, Primary Examiner.

D. R. VALENTINE, Assistant Examiner.

U.S. Cl. X.R. 204-228

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