Control Device For Two Metallic Salt Components In Electroplating Baths

Abstract

A device for controlling two metallic salt components in an electroplating bath has a sensor for the bath concentration, a sensor for the bath density, two conveyers for supplying respective components into the bath, and limit switch circuits actuating the respective conveyer in response to predetermined indications of the sensors.

Description

BACKGROUND OF THE INVENTION

The invention relates generally to a device for controlling electroplating baths. More particularly, the invention relates to a device for controlling two metallic salt constituents in an electroplating bath the density of which is substantially determined by its total salt content, and which is provided with a first sensor for detecting the concentration of one of the two components, with a second sensor for aerometrically detecting the density of the bath, and with an arrangement for determining the concentration of the other components as the difference between the indications of the two sensors.

It has been known how to determine the salinity of electroplating baths of the above mentioned type by means of so-called wet analysis. Wet salinity is determined by measuring the conductivity of the bath. The disadvantage of such conventional method resides in that its applicability is considerably limited by the following operating conditions: the total salt content can be accurately determined only when the solution contains only one metal salt component; or if all components in the solution change approximately at the same ratio; or if there prevails the change of one component in the solution.

There have been known also other embodiments of the measuring and controlling devices for electroplating baths such as described, for example, in the DDR Pat. No. 68,120. These known devices, however, have a very complicated structure and inconvenient adjustability for various bath compositions and, consequently, they are not fully satisfactory for various controlling programs.

It is therefore an object of this invention to avoid the disadvantages of prior art. More particularly, an object of this invention is to provide a control device for electroplating baths having two metal salt components the density of which is determined predominantly by the total metal salt content, which makes it possible to supply individual components of the bath in arbitrary proportions in response to a preset nominal value of the content of those components.

Another object of this invention is to provide a control device of the aforementioned type which enables an instant and automatic adjustment of two components of the electroplating bath in response to changed conditions of the latter.

SUMMARY OF THE INVENTION

According to the present invention the above objects are attained by providing switching circuits having nominal or desired value adjusting means for each of the aforementioned sensors, conveying devices for the two components, the driving means of the conveying devices being in circuit relation with power supply and switching circuits in such a manner that each of the conveying devices is in series connected to a limit switch which closes when the density indication falls below a predetermined value. This switch cooperates with another (second) in series connected switch coupled to the first sensor for measuring the concentration, thereby actuating the conveying device for one component. The other conveying device is actuated by the latter switch when the indication of the sensor for detecting the concentration of one component of the bath falls below a predetermined nominal value. It is advantageous if the second switch is carried out as a two-contact switch which, when being in an actuated position closes the power supply circuit for one of the conveying devices and in its actuated position closes the feeding circuit for the other conveying device.

In a further development of this invention, the controlling arrangement is provided with a third sensor for detecting the temperature of the bath, connected to a third limit switch circuit having a switch connected in series with the first and second switches to interrupt the feeding of the conveying devices and thus the supplying of the components into the bath if the temperature of the bath is out of a predetermined critical temperature range. The limit switch circuits are equipped preferably with switching indicators or measuring instruments having adjustable limiting or stop contacts on their scales.

In order to enable visual checking of the operation of the arrangement, the device is provided with signalling circuits associated with respective limit switch circuits to indicate visually the operation of individual conveying devices. The signal lamp of each signalling circuit is preferably connected to a two-position switch which is controlled by the first limit switch circuit connected to the density sensor. The signal lamp for indicating the preset critical temperature range of the bath is connected across the series of limit switches controlling the conveying devices, and is actuated together with a limit switch controlled by the temperature sensor.

The advantages attained by the invention reside particularly in the fact that the resulting device has a universal applicability. By means of the device of this invention it is possible to control and adjust any combination of metallic salts without complicated and time consuming wet analyses or without the reconstruction of the measuring and controlling device. This advantage is particularly important for small workshops which hitherto, due to the small amount of processed pieces and due to the size of electroplating baths, have not been in a position to provide for each electroplating process a special bath.

BRIEF DESCRIPTION OF THE DRAWING

For a better understanding of the invention, together with other and further objects and advantages thereof, reference is made to the following detailed description of the single FIGURE of the accompanying drawing, which FIGURE is a schematic diagram of a control device for adjusting two metallic salt components in electroplating baths according to this invention.

DETAILED DESCRIPTION

Referring now to the drawing, a measuring cell 1 which is located preferably in a branch part of a tank 1' for an electroplating bath 26 is provided with a first sensor consisting of electrodes 3 and 4, a second sensor 2 for areometric detection of the density, and a third sensor 5 for detecting the bath temperature.

The sensor 2 supports on its top a metal segment 20 which enters a coil of a measuring bridge 21 (inductive measurement). It is, of course, possible to employ other types of conversion, such as capacity measurement or pick-up, for example.

To screen the measuring cell 1 against outer disturbances, the entire measuring cell 1 is surrounded by a grounded metal lattice 6. Connecting conduits 7' and 7 are designed for connecting the measuring cell 1 to the corresponding outlets in the tank 1' of the proper electroplating bath 26.

The electrodes 3 and 4 of the first sensor are connected via an amplifier 10 to a switching device 8 which has adjusting means (preferably limit stops) for adjusting the nominal or desired value of the first sensor (electrodes 3 and 4). The second sensor 2 is connected via the measuring bridge 21 (without the employment of an amplifier) to a second switching device 9 which is also equipped with an adjuster for setting the limit or desired value of the second sensor 2. Advantageously, the switching devices 8 and 9 are made in the form of measuring indicators having adjustable limit stop contacts 8' and 9', each being adjustable in its position with respect to the pointer of an indicator, as indicated by double arrows in the devices 8 and 9.

The switching device 9 closes in response to the indication from the output of bridge 21 its contact relay 14, which energizes the relay 24 and closes the relay contact 15. Provided that contact 16 is closed, as will be described below, the power supply circuit O and R is connected through one contact of the switch 13 to a conveying device 23 provided for conveying through a conduit 30 the other of two metallic salt components into the electroplating bath 26'.

On the other hand, the switching device 8 closes through relay contact 12 the energizing circuit O and R for the relay 19 which, in turn, switches over to the other contact of the switch 13, thereby stopping the conveying device 23 and actuating another conveying device 22 for the first metallic salt component. It will be understood that the relays 19 and 24 serve merely for the amplification of controlling or switching pulses of the switching contact 14 and 12 pertaining to switching devices 9 and 8.

Parallel to the double pole switch 13 there is arranged a similar double pole switch 13' which controls signalling devices 22' and 23', operating in a similar manner as the switch 13 controls the conveying devices 22 and 23, thus visually indicating the operation of an actuated conveying device.

In the shown embodiment, the conveying devices 22 and 23 can operate only when a temperature measuring and switching device 17 which is coupled to the temperature sensor 5, maintains the switch 16 in its closed position. The limit switching and temperature measuring device 17 can be adjusted to indicate a predetermined critical temperature range of the bath. Simultaneously with the switch 16, the device 17 controls a switch 16' connected across the clamps of a power supply circuit O and R. The switch 16' controls the actuation of a visual signalling device 18.

The mode of operation of the control device for adjustment of two metallic salt components in electroplating baths 26 of the invention will be explained by way of an example in connection with a nickel bath. In a nickel bath of conventional composition (Watts-type) there are contained two metallic salts, namely nickel chloride and nickel sulphide. If the second sensor 2, which areometrically detects the density of the bath, displaces the pointer of the limit switch indicator 9 beyond a predetermined position corresponding to nominal or desired value of the total concentration of the metallic salt in the bath, the switching relay contact 14 closes the feeding circuit for the relay 24 and, consequently, the relay contact 15 becomes also closed. Provided that switch 16 is in its closed position and switch 13 is in its unactuated or normal position closing the right hand contact connected to the conveying device 23 for supplying nickel sulphide, the latter conveying device becomes actuated and the nickel sulphide component will be supplied into the bath. The double pole switch 13, as illustrated, actuates the conveying device 23 in its rest position which occurs only when the switching device 8, adjusted to the desired or nominal indication of the first sensor (3 and 4) for the detection of the nickel chloride content in the bath, fails to indicate any deviation from the nominal value of the nickel chloride concentration. Should the electrodes 3 and 4, however, detect any deviation from the preset nominal value of the nickel chloride, the first switching device 8 will become actuated, the switch 12 closes and the limit switch indicator 19 displaces the switch 13 to the left hand position, thereby energizing the conveying device 22 for nickel chloride. The conveying of nickel chloride or of nickel sulphide can be attained only when the temperature controlling switch 16 is in its closed position. The latter condition exists when the temperature sensor 5 in connection with the nominal adjustor 17 detects a preset range of tolerances for the temperature of the bath. Parallel to the series connection of the switches 15 and 16 there are arranged switches 13' and 16' controlling signalling devices 22', 23' and 18, designated for visual observation of the operation of the device.

In the illustrated device according to the invention, the sequence of controlling steps is as follows: the conveying device 22, such as for example a conveying pump, first refills the nickel chloride until its desired concentration is attained and the contact of the switch 13 is displaced. Subsequently, there follows the addition of nickel sulphide until the nominal or desired value of the total metal salt contact is detected and the switch 15 is opened. If, however, the bath temperature is not in the predetermined range of tolerances, the switch 16 prevents the aforementioned regulation of the bath concentration unless the bath is reset to its predetermined temperature condition.

Further modifications will also occur to those skilled in the art and all such are considered to fall within the scope and spirit of the invention as defined in the appended claims.

Claims

Having thus described the invention, what we claim as new and desire to be secured by Letters Patent, is as follows:

1. A control device for controlling the supply of two metallic salt components in an electrolytic bath the density of which is defined substantially by its total salt content,

comprising, in combination,

concentration sensing means operable for detecting the concentration of one of said two salt components in said bath,

density sensing means operable for areometrically detecting the density of said bath,

first limit switching means preset for a nominal indication of and controlled by said concentration sensing means,

first conveying means operable for supplying said one salt component into said bath,

second conveying means operable for supplying said other salt component into said bath,

said first switching means cooperating with said conveying means so as to activate said first conveying means when the concentration of said one component within said bath falls below said nominal indication and, alternatively, said second conveying means when said concentration sensing means detects the concentration of said one component corresponding to said nominal indication, and

second limit switching means connected in series with said first switching means and controlled by said density measuring device to inactivate both said first and second conveying means when the density of said bath exceeds a preset limit value.

2. A control device according to claim 1, wherein said first limit switching means includes a double pole switch for alternatively connecting said first and second conveying means to respective poles of said first limit switching means, and said second limit switching means includes a single pole switch connected in series with said double pole switch for energizing either conveying means when actuated.

3. A control device according to claim 1, further comprising temperature sensing means, third limit switching means adjustable for a critical temperature range of said bath and controlled by said temperature sensing means for interrupting said first and second limit switching means.

4. A control device according to claim 3, further comprising a third signalling circuit actuated by said third limit switching means.

5. A control device according to claim 1, wherein each of said first and second limit switching means includes a limit switching indicator.

6. A control device according to claim 5, wherein said limit switching indicators are adjustable.

7. A control device according to claim 1, further comprising two signalling circuits respectively connected in parallel with said first and second conveying means and controlled by said first limit switching means.

8. A control device, as claimed in claim 1, comprising an electric circuit including several branches, one of said branches including said concentration sensing means, another branch including said density sensing means, and a third branch including a temperature sensing means, all of said sensing means being immersed in said bath, a limit switching means connected in each branch, a fourth branch including said limit switching means in series, the limit switching means of said concentration sensing means having a double pole whereby when contact is made with one pole one of said conveying means is energized to supply one salt component to the bath and, respectively, when contact is made with the other pole the other conveying means will supply the other salt component, when the fourth branch is uninterrupted.

9. A control device according to claim 1 further including setting means for adjusting switching limits of said first and second switching means, respectively.