US 3852170 A
A method and apparatus for bar electroplating including continuously supplying a plurality of bars successively; cleaning the surface of the bars to be plated; heating the bars up to a plating temperature and accomplishing the bar plating operation by feeding the bars along a straight path through an electrode immersed in an electroplating tank.
Claims available in
Description (OCR text may contain errors)
Un ted States Patent 1 1 1111 3,852,170 Angelini Dec 3, 1974 1 1 METHOD AND APPARATUS FOR  References Cited CARRYING OUT CONTINUOUS THICK UNITED STATES P N CHROME PLATING F BAR, WIRE AND 781,867 2/1905 Aylsworth 204/210 TUBE, BOTH EXTERNALLY AND 1,803,691 5/1931 Brockway 204/210 INTERNALLY 2,756,205 7/1956 Rosenquistm 204/209 2,825,681 3 1958 Johnston 1 ..204/28  Invent: Sergm Angel, M113, Italy 3,616,287 10/1971 Draghicescu et a]. 204/  Assignee: B.E.S. Brevetti Elettrogalvanici 3720595 3/1973 f' 204/206 superfiniture SDAI, 3,751,344 8/1973 Angel1n1 204/26 Eh-L' ht t",L' ht t' Sc en lec ens em lee ens em Primary Examiner-T. M. Tufariello Flledl 1973 Attorney, Agent, or Firm-Fidelman, Wolffe, Leitner 21 Appl. No.: 329,220 & Hmey Foreign Application Priority Data Feb. 8. 1972 Italy 20337-A/72  ABSTRACT Related Application Data A method and a aratus for bar electroplatin includ- 63 PP s 1 1 fgg g g g r gzi 5 fig ing continuously supplying a plurality of bars succes- 9 A um sively; cleaning the surface of the bars to be plated; 5' d one heating the bars up to a plating temperature and accomplishing the bar plating operation by feeding the $3 4 5 bars along a straight path through an electrode im-  Field 61 Search 204/210, 25, 27, 28, 206, mersed electroplatmg tank' 204/209v 21 Claims, 22 Drawing Figures S: /////////////////////1// 1//////////// 1 ://2 k\ &1\\\\\ \\k\\\\\\\\\\\\\\\\\\\\Y\ PATENTEU E 1974 SHEET 2 OF 5 mammal: 3,852,170
SHEET NF 5 The present invention is a continuation-in-part of application Ser. No. 89,428, filed Nov. 13, 1970, and now US. Pat. No. 3,751,344, and application Ser. No. 261,419, filed June 9, 1972 now abandoned.
This invention relates to a method and apparatus for electroplating, coating or metalization of general bars. More particularly, the present invention relates to chrome plating bars of circular cross-section as well as those that are of different cross-section.
The invention will be hereinafter set forth and described with reference to a method and apparatus for metal bar chromium plating. It should be understood, however, that the invention is not limited thereto and can be extended and used to provide a metal coating on bars by an electrolytical deposition process.
As is well known, in present bar chromium plating systems, provision is made for a tank containing a chromium plating bath. The tank is longer than the bars and the bars are immersed in the bath for a predetermined time period. These systems are extremely cumbersome and expensive due to their size requirements for the tanks. Moreover, the chromium plating is accomplished in a batch method with the resulting low hourly output of chromium plated bars.
Further disadvantages arise due to scrap produced by an inability to chromium plate the portion of the bar gripped and clamped by the lifting apparatus required for immersion of the bars in the tank. Further, due to the deflection of said bars caused by the weight thereof, the distance between the electrodes and bars varies and non-uniform deposition of the chromium coating or plating occurs. The thickness is not uniform or constant longitudinally, increases from the center to the ends and varies circumferentially in accordance with the arrangement of the electrodes within the chromium plating bath.
Therefore, an object of the present invention is to provide a method and apparatus for bar electroplating, and particularly chromium plating for bars and the like, capable of overcoming the above mentioned disadvantages.
More particularly, the invention relates to a method and apparatus for continuously electroplating bars and the like.
Generally, the method according to the invention includes the steps of continuously supplying a plurality of bars consecutively to an electroplating bath; cleaning the surface of the bars to be plated; heating the bars up to a plating temperature and electroplating by feeding the bars along a straight path through an electrode immersed in an electroplating bath.
Particularly, a first preheating step for each bar can be carried out upstream of the plating bath by utilizing the plating current. Then a next heating step can be carried out within the plating bath prior to the plating step by heat transfer from the bath. The bars thus enter the plating electrode at a temperature substantially corresponding to that of said plating bath.
More particularly, the present invention relates to a method for chromium plating either cylindrical or noncylindrical section bars, wherein the bars are continuously supplied to a chromium plating bath in two or more straight paths parallel to and spaced apart from one another, so as to substantially increase the hourly output of the bath.
A further object of the present invention is to provide a method and apparatus for bar electroplating, and particularly for bar chromium plating, wherein the spacing between the bar to be chromium plated and the anode in the chromium plating bath is maintained constant so as to substantially improve the metal coating deposition on the bars by controlling coating thickness to very close tolerances. Thus, subsequent grinding of the electroplated or chromium plated bars conventionally can be avoided.
The invention is also directed to a general plating system, and particularly to a chromium plating system for bars and the like, wherein the floor space required is minimized in that the chromium plating tank length is substantially less than that of the bars to be processed and wherein, by suitable expedients, tube or noncylindrical section bars of differentdiameters can be processed. This is afforded by using special seals at the common axis; (4) sealing means for the moving bars at each of the passage openings in the tank to resist, and preferably prevent, any egress of processing liquid whereby a constant liquid level is maintained; (5) means for supporting, guiding and successively feeding the bars through said electroplating bath or tank along said axis; (6) means for causing a current to flow between said electrode and the bars to be plated; (7) means for cleaning and heating the bars to a plating temperature upstream of the electrode in said tank; and (8) means for. feeding and recycling the processing liquid between the electroplating tank and a supply reservoir while maintaining it at a constanttemperature.
By adjusting and maintaining the processing liquid at a constant temperature and by heating the bars prior to entering the plating electrode, a smooth and constant plating operation is promoted, thereby providing bars having substantially constant characteristics of the coating layer produced along each of the bars and on different bars.
The system is also provided with means for recirculating the washing water, as well as the processing liquid, for the bars at the tank outlet. A means is also provided for purifying the fumes or vapors from the processing bath.
These and other features of the method and system according to the invention will become more apparent from the following description when taken in conjunction with the attached drawings, in which:
FIG. 1 is a general view of a system according to the invention which, due to drawing requirements, has been divided into three portions joining at the division lines aa and bb, the three portions being indicated as 1A, 1B and 1C;
FIG. 2 is a view taken along line 22 of FIG. 1;
FIG. 3 is a partial sectional view showing, on an enlarged scale, a detail of the electroplating tank on the entry side for the bars;
FIG. 4 is a longitudinal sectional view of a box for the electrode contact to the bars to be processed;
FIGS. 5 and 6 are longitudinal and cross-sectional views, respectively, showing a second embodiment of a box for the electric contact to the bars;
FIG. 7 is a longitudinal sectional view of a pneumatic sealing device located at a passage opening for the bars in the processing tank.
FIG. 8 is a view taken along lin 8-8 of FIG. 7;
FIG. 9 is a side view showing a bar drawing device;
FIG. 10 is a front view of the device shown in FIG.
FIGS. 11, 12 and 13 are exploded, side and front views, respectively, of a bar cleaning device for cylindrical bars;
FIG. l4 is a diagram of the device used for removal of the fumes and vapors from the electroplating bath;
FIGS. 15 and 16 are fragmentary cross-sectional and longitudinal views, respectively, of a modified system according to the invention;
FIG. 17 is a front view showing a particular scaling for non-circular section bar electroplating FIG. 18 is a' vertical sectional view taken along line 18-18 of FIG. 17; and
FIGS. 19 and 20 are different views for a detail of the sealing device shown in FIG. 17.
Referring now to FIGS. l-3 of the accompanying drawings, it will be seen that a continuous electroplating system according to the invention, particularly for barchromium plating, comprises a tank designated as a whole at 29 which contains a processing liquid forming the electroplating bath. The metal bars 10 which are to. be plated are continuously passed through this tank and are successively mechanically and/or electrically interconnected and fed along one or more straight paths parallel to, and spaced apart from, one another by means of a suitable drawing device, such paths lying on a horizontal plate as shown in FIG. 2.
More particularly, in the course of their feeding, these bars 10 are carried at both ends of the electroplating tank 29 by stands 1 l at the top having a support or bracket 12 being carried at the upper end of a vertical screw 13 which rotates in a nut screw 13', operable by handle bars 13" to adjust the correct height position of support 12 for maintaining said bars 10 at accurate rectilinear attitude.
The bars are connected together in accord with Pat. No. 3,751,344, by means of e.g. threaded or friction fittings. The fittings may be conductive or nonconductive depending on considerations such as bar length, etc. Also, the bars may be of circular crosssection, triangular cross-section, rectangular crosssection or other cross-section, however irregular in shape. Different seal means as disclosed herein may be required for differing cross-sectional bars.
The drawing or feeding of bars 10 to the processing tank 29 is accomplished by a drawing device which, in the example shown in FIG. 1, is located upstream of the processing tank 29 as shown by the bar movement direction according to arrow A, but which could also be downstream of said tank.
The bar drawing device substantially comprises a first frame 16, adjustable in height and carrying the lower drawing rollers 17. Further, upper drawing rollers 18 are supported on a second .frame 19 adjustable in height relative to first frame 16. Thus, correct positioning and smooth drawing of the bars can be accommodated independently of the diameter thereof.
For height adjustment of the first frame 16 carrying the drawing device, from FIGS. 1 and 2 it can be seen that vertical screws 14 are provided as rotatably carried by frame 16 and meshing with corresponding nut screws 14' rotated in pairs by corresponding worms operable by a crank.
Similarly, frame 19 is adjustable in height relative to frame 16 by screws 20 secured to said frame 16 and meshing with corresponding nut screws 20 (FIG. 2), rotatably carried by frame 19 and rotatably driven by suitable worms or the like operated by cranks 160.
The above mentioned lower and upper drawing rollers l7 and 18, respectively, are rotatably driven by a geared motor unit 21, carried by frame 19, through a speed variator 22, of which drive shaft 22' carries at its ends pulleys or gear wheels driving, through belts or chains 22, the pulleys or gear wheels 161 and 162 of the bearing shafts of said drawing rollers 17 and 18. Thus, the drawing speed can be varied and adjusted in accordance with the diameter of the bars to be processed and the thickness of the material to be formed on the bars.
As shown in FIG. 2, drawing rollers 17 and 18 are coated with a layer of relatively resilient material, have a circumferential grooveformed therein for bar guiding, and are aligned with the feeding axis of the bars. This groove should be slightly distorted when in contact with the bar to increase thefriction surface,
thus avoiding slippage and allowing for accommodation of bars of different diameters.
The bar drawing device could be adapted for drawing one or more bars, such as parallel bars 10 shown in FIG. 2, or plural bars at one roller as schematically shown in FIGS. 9 and 10, where the drawing rollers 17 and 18 have been made with conical surfaces converging to the center in order to increase the bar adhering surface. v
The bars, continuously fed to the processing bath in tank 29, first pass through box 23 wherein electric contacts are arranged for connecting the bars to the negative pole of a DC. power supply. Thus, the bar portion between anode electrode 31 (FIG. 3) and the electrode 131 (FIG. 16) is charged with the required current flow for the deposition of material, such as chromium, on bar 10. A similar contact box 23' may be provided at the outlet or downstream of tank 29, as shown in FIG. I.
The plating current flowing through the section of bar 10 between the upstream contact box 23 and the anode 31 is preheated by the current to a temperature determined by the electric resistance of the bar path and the square of the intensity of current flowing through the bar.
It is important to provide a positive electric contact surface with the bars while interferring with the feeding thereof to the least extent possible. This has been accomplished by the contact box of FIG. 4 wherein the electric contact with bars 10 is provided by copper plaits 24 arranged about the peripheral surface of the bar 10. The plaits 24 are clamped against bar 10 by two opposing tile-like elements 25, the latter being held in proximity to each other by resilient rings 25a or other suitable means and being of a predetermined internal shape corresponding to the number of plaits 24 and the bar diameter.
Downstream of contact box 23, the bars pass through a cleaning device 26 which comprises a sleeve containing an abrasive material mat or felt 27 (as shown in the cut-away portion of FIG. 3) completely surrounding bar 10. The material 27 cleans bar 10 by, e.g., rubbing.
In order to remove any possible impurities from said cleaning device and bar, the sleeve is supplied with hot water at a predetermined pressure through a conduit 28. The water continuously removes deposits from the bar surface or from the cleaning felt. The use of hot water for cleaning devide 26 is advantageous since it helps retain bar 10 at its preheated temperature as mentioned above. Therefore, in order to collect water dripping from cleaning device 26 or from a plurality of such cleaning devices where the bars are fed along two or more parallel paths as shown in FIG. 2, a tank 27' is provided underneath the cleaning'device or devices 26 as shown in FIG. 1B. This tank 27 collects the water coming out of cleaning device 26 and conveys it through a pipe 27 to a collection tank 40 which is provided with a net cover 41 at the top thereof for carrying a filter 41', so that impurities are retained on filter 41. and conditioned water enters said tank 40. The water is withdrawn from tank 40 through pipe 43 and recycled by pump 43'.
As stated, bars 10 pass through the tank 29 containing the plating bath. Therefore, passage openings for bars 10 provided on the opposite walls 29' of the processing tank 29 are fitted with suitable sealing devices 30 to resist,and possibly inhibit, any exit of processing liquid from the tank. Thus, a constant'liquid level L is maintained above bar 10 and tubular electrode 31 as shown in FIG. 3.
These sealing elements 30 will be further discussed in connection with cylindrical bars (FIG. 7) and noncylindrical section bars (FIGS. 17-20).
Upon continuously moving, the bars 10 enter the processing tank 29 through the sealing device 30 on end wall 29, and travel'a section or length h in the tank between the inlet opening and electrode 31. During this travel, the bar 10 is heated up to the plating temperature, preferably the temperature of the processing liquid, by heat transfer from the liquid. The bar then enters and passes through the perforated tubular electrode 31 where the plating is carried out by deposition of a layer of predetermined thickness, depending on the bar feeding rate and the intensity of the plating current.
The plated bars pass through a corresponding sealing device 30 in exit tank wall 29' which is fully similar to the above mentioned devicenThey are then washed with water supplied by a nozzle 34. The plated bars pass through a second contact box 23, which also supplies current, so that plating current is supplied at both ends of tank 29 and the bar temperature is partly retained at the tank outlet to aid in the drying step. Following contact boxes 23, the bars (carried by one or more supporting stands 11) may be further processed as desired. 1
the washing water and conveying it through a conduit 44 to a collection tank 45. Tank 45 is manually identical to tank 40 mentioned above and is provided with a filtering device 41' and 42. The water is withdrawn Downstream of tank 29 and underneath the washing f, water nozzle 34, a basin 44 isprovided for collecting from tank 45 by means of a pump 46 and supplied by a two-way valve 47 either to nozzle 34 or to an external reservoir, according to process requirements.
Similarly, in order to collect any processing liquid lost from tank 29 through sealings 30, collection basins 30' are provided upstream and downstream from the tank under the seals. Conduits 30" collect the lost fluid and convey it to a cooling tank 32 for the processing liquid, the processing tank 29 usually being connected to tank 32 by a loop or closed circuit.
More particularly, plating tank 29 is connected through a gated conduit 35 to tank 32 wherein the liquid is maintained at a predetermined level above a cooling coil 32 suitably connected to a refrigerating system (not shown). Tank 32 is provided with a thermostat 36 driving the refrigerating system for automatic temperature control and a tap or cock 38 for total discharge. It is also connected by a pipe 37 (partially shown in FIG. 1) with a tank (not shown) of a higher capacity than that of the processing tank 29 which is connected through suitable pumps and pipes to tank 29 for the recycle of the processing liquid. Thus, processing tank 29 can be continuously supplied with processing liquid of the desired composition and temperature, as the addition of further electrolyte can be directly effectedto the above mentioned general or major tank. The use of the cooling coil 32' for the liquid exiting from processing tank 29 is required since the processing liquid will, in the course of plating operation, be heated and thus have to be cooled prior to recycling for correct control of the processing bath temperature.
The sealing devices 30 onthe end walls 29' of the processing tank may be of any type, e.g., the pneumatic seals more fully described in connection with FIG. 7.
When the sealing devices 30 are of the pneumatic character, the system is provided with a compressed air supply (not shown), this supply being connected through a conduit 48 to the pressure regulator 50 and distributor 49 which, in turn, is connected to several pneumatic sealing devices.
As shown in FIG. 1, the processing tank 29 is covered with a suction hood 51 and 151 which, as shown also in FIG. 14, is connected by exhaust fan 153, conduit 152, and fume removing device 154 to a stack for conveying the vapors to atmosphere.
As shown in FIG. 14, conduit 152 has an intermediate section 152' sloping to the hood for condensate return, as indicated by the broken arrow. Thus, thorough purification of the fumes or vapors from the processing tank can be provided along with recovery of the electrolyte carried by such fumes by water washing. The wash water exits from device 154 through a bottom conduit 155 and can be recycled.
Refering now to FIGS. 5 and 6 of the attached drawings, a different embodiment of the contact box will be described. In the embodiment of 'FIGS. 5 and 6, the contact box comprises a hollow cylindrical body 230 which has two sealing devices 25 at the ends thereof, such as those'of the pneumatic character hereinafter described, through which bars 10 continuously pass. A chamber 25" is formed by sealing devices 25' and cylinder 230, with ingress and egress being provided by upper aperture 23a, the chamber thus being sealed with respect to the passing of bars 10. A copper strap cathode C is passed through upper aperture 23a of chamber 25 takes on the circular shape of the container body, and joins itself outside aperture 23a. By
introducing mercury M (FIG. 6) into the space of chamber 25", positive electrical contact is provided along the bar circumference for the plating current.
A longitudinal section of a pneumatic sealing sleeve useful at the inlet and outlet openings for the bars in processing tank is shown in FIG. 7. In this Figure, the sealing sleeve substantially comprises a hollow cylindrical'body 30, coaxially with cylindrical bars 10, through which the bars to be processed pass. At its ends, hollow cylindrical body 30 has circular openings 56 coaxial with the bar passage. A tubular plastic acid resistant material 57 e.g., an acid resistant rubber, is attached and sealed to openings 56 at its ends and, along with body 30, formsa hermetically sealed annular chamber 58. This chamber 58 communicates with a pressurized air supply through a conduit 59 distributor 49, pressure regulator 50, and conduit 48 (see FIG. 18). Thus, by passing bars through tubular diaphragm 57 in the sealing sleeve 30 and supplying chamber 58 with air pressure, diaphragm 57 is urged toward the surface of bar 10 and provides a positive sealing for the processing liquid in tank 29. Moreover, while providing for a seal on bar 10, diaphragm 57 will not inhibit the sliding thereof. The use of a pneumatic sealing sleeve also allows for the accommodation of bars .of different diameters without the replacement thereof. However, it is apparentthat for bars of substantially different diameters, sealing sleeves of different sizes should be employed.
Sealing device 30, and more particularly the above mentioned sealing sleeve, can be fixedly attached to end walls 29' of the processing tank when the latter is to be used for electroplating the same type of bars at all times, or can be detachably and readily, replaceably secured (as shown in FIG. 8) when the material to be plated varies. As shown in this Figure, sealing device 30 can be carried by a plate 60 and positioned within a channel or U-shaped seating 61 formed along the edge of a saddle-like notch 61 provided on each wall 29 of the processing tank 29 when in use. Thus,.one tank can be used for processing bars having different crosssectional shapes and sizes.
However, the sealing device 30 can also be of the plate type, as described below in connection with a modified form of the invention. Of course, along the edge 60 of tank 29 provision should be made for a suitable seal for the liquid in the tank.
Referring now to FIGS. 11, 12 and 13 of the attached drawings, an exemplary structure for the cleaning device 26 will be described.
As shown, this device comprises two yoke-shaped elements 62 of substantially symmetricalconstruction, each having a semicircular notch containing an abrasive felt 27 or other appropriate material. The two yoke-shaped elements 62 are attached to each other by any suitable clamping device, for example, resilient binding 63 shown in FIG. 13. Upper yoke-like element 62 is also provided with a conduit 28 for admission of wash water, as above set forth. A bracket 64 partially surrounds upper yoke-like element 62 and is provided with an arm 65 which is connected to the stem 66 of a pneumatic or oleodynamic type of double-acting cylinder 67. Movement of the piston by fluid pressure from a source which is not shown provides reciprocating rotation for effective operation of the cleaning device. If desired, cleaning device 26 could be continuously rotated rather than alternatively rotated.
Referring now to FIGS. and 16, a schematic modified form of the system according to the invention will be described. In these Figures, all of the devices or parts common to FIG. 1 have not been shown for the sake of simplicity. As shown, the processing tank 116 has been herein placed with a second tank 117 of a larger size in order to allow for electroplating tubes, circular cross-section bars and non-circular crosssection bars. Thus, a particular plate sealing device has been designed for the latter.
The bottom 116' of processing tank 116 is elevated from the bottom 117' of the outer tank and is supported by legs 118. Outer tank 117 is of a higher capacity than the inner tank 116 and the liquid in tank 117 is maintained at a level L below'the bar passage openings in its walls, while inner tank 116 is completely filled with the processing liquid. The processing liquid is maintained at a predetermined temperature by heating elements 119 and is continuously'recycled by means of pumps 120 and 120 so that the liquid level in tank 116 is substantially constant and above the bars which are to be processed. i
In order to reduce heat loss in the processing liquid in outer tank 117, covering baffles 121 are provided between adjacent walls of the tanks. The baffles are located below openings 123 through the inner tank and are retained spaced apart from the inner tank adjacent the .openings to allow the passage into the bottom of tank 117 of the processing liquid which leaks from the sealing devices 126 and overflows from the top edge of the inner tank. To this end, the upper edges 116" of inner tank 16 adjacent the seals are relatively lower than the rest of the tank edges, so that the liquid exhaust and overflow will occur in this zone.
Of course, openings 122 and 123 in the two tanks should be aligned with one another along a common axis for the bar or section electroplating operation. A tubular anode 131 is located within inner tank 116 and completely'immersed in the processing solution.
The double tank can be used for electroplating bar stock where a pneumatic sleeve sealing of the above described character could not be used. However, it is apparent that instead of the double tank system, the system as shown in FIG. 1 could be used, providing end tanks 30' of higher capacity than shown for collecting the processing liquid.
In FIGS; 17-20, a further embodiment for sealing processing tank 29 or 116 when plating various crosssection bars is shown. As shown in the Figures, bar 138 is surrounded throughout its profile by a double row of flexible blades 139. The blades of each row are located at equal short spacings from one another and staggered relative to the blades in the adjoining row, so that one blade 139 in a row will bridge the spacing between two adjoining blades 139 in the other row Thus, the whole openings 123 is obstructed by the double rows of blades interferring with the exit of the processing liquid from inner tank 116, and thus allowing the maintenance of substantially constant liquid level in the tank, since the tank is continuously supplied with an amount of liquid equal to the amount of liquid existing laterally and at the bottom of the bars. Blades 139 are secured to edge 123' of opening 123 on three sides, while at the g top of the tank, the blades 139 are secured to lower edge 140' of a gate or sliding plate 140. The plate is slipped into and positioned by grooves 124' (FIG. 17). By moving plate 140, the position of blades 139 can be controlled, and thus the closure of opening 123 can be regulated to control liquid exit. Plate 140 is provided with means to fix its position (not shown) as desired, for example, by clamping screws or other equivalent means. Further, as shown in FIG. 19, at the lower edge of opening 123 the blades will intersect one another and further inhibit liquid loss.
Opening 123 could also have the lower portion, as well as the blades on plate 140, in the form of oppositely corresponding arcs so as to direct said blades 139 to the geometrical axis of the bars 138 to be processed. Of course, blades 139 of FIGS. 17-20 should be made of an acid resisting, relatively resilient and flexible material in order not to be attacked by the processing liquid in the tank and to maximize liquid retention.
Referring to FIG. 1, the operation of the apparatus according to the invention is substantially as follows:
Bars are successively mechanically and/or electrically interconnected and carried by stands 11. They are fed to processing tank 29 after first passing through the contact box 23, then through cleaning device 26, and finally through seal 30 in tank 29. In the tank, the bars are immersed in the processing liquid contained in anode 31 and are coated by electroplating. The coated bars emerge from end wall 29' of the tank, through seal 30 and are washed, dried and then further processed as desired.
As mentioned above, in the course of the first travel path of each bar between contact box 23 upstream of tank seal 30, a first preheating of the bar is effected at a lower temperature than the electroplating temperature by the flow of the electroplating current through the bar. Also, in the length or section h within the tank between end wall 29' and the tubular anode 31 adjacent thereto, a second heating step for bars 10 is effected so that the bar temperature is substantially the same as that of the processing liquid in the electroplating bath. By way of example, a'length or distance h of about 50cm (20 inches), depending on the feed rate of the bar, usually provides for proper heating of the bar. The plating bath temperature may vary in accord with known ranges.
Thus, a process for operating under optimum working conditions is disclosed herein, in which a continuous electroplating system functions with high hourly output and produces coatings which are within strict tolerances along each bar and between different bars. Moreover, the particular system herein described allows for the maintenance of a substantially constant temperature in the bath and has the advantage of avoiding any pollution because of the liquid recirculation and/or the purification of the fumes or vapors from the processing bath.
What is claimed:
1. A method for continuously electroplating a plurality of elongated bars in a plating comprising:
a. mechanically attaching said bars together by couplings of the same section as said bars to provide a generally continuous electroplatable surface;
b. serially cleaning said attached bars prior to plating by passing said bars consecutively through a cleaning medium;
c. serially passing said bars into contact with an electrode whereby said bars are charged with anelectroplating current;
d. serially heating said bars to the temperature of said bath prior to plating;
e. serially passingsaid bars through said electroplating bath and in the proximity of an electrode whereby said bars are electroplated; and
f. serially passing the plated bars out of said bath.
2. The method of claim 1 wherein said preheating is effected by first preheating said bars outside said bath and by secondly preheating said bars in said bath prior to'the plating step.
3. The method of claim 2 wherein said first preheating is effected by said electroplating. current.
4. The method of claim 3 wherein said second preheating is effected by the contact of said bath with said bar prior to electroplating.
5. The method of claim 3 wherein said mechanical connection is additionally an electrical connection.
6. The method of claim 1 wherein said electrode in said bath is a tubular electrode positioned co-axially with said bars.
7. The method of claim 1 wherein said bars are additionally cleaned after passageout of said bath.
8. The method of claim 7 wherein said cleaning after plating includes washing.
9. An apparatus for continuously electroplating a plurality of elongated bars comprising:
a. means for serially mechanically attaching said bars together;
b. aligning means positioning said attached bars along an axis;
c. cleaning means prior to electroplating for cleaning said aligned bars;
d. drive means causing said bars to traverse the line of said axis; 7
e. a plating tank containing plating liquid and having seal means on two ends .thereof positioned coaxially with the axis of said bars whereby said bars pass serially into said tank through first seal means,
through said tank and out of said tank through said sealmeans;
f. heating means for said bars for heating said bars prior to electroplating in said tank to the temperature of said plating liquid prior to electroplating;
g. a first electrode positioned outside said tank and a second elongated electrode positioned inside said tank whereby said electrodes cooperate to provide an electroplating current to plate said bar with material in said plating liquid, said electrodes being positioned coaxially with said bar, and said first electrode being in electrical contact with said bar before said bar enters said tank while said second electrode is spaced from said bar.
10. The apparatus of claim 9 wherein said heating means includes the current passed along said bars by said electrodes.
11. The apparatus of claim 9 further including second cleaning means for cleaning said plated bars.
12. The apparatus of claim 9 further including recycle means for recycling lost plating liquid to said plating tank.
13. The apparatus of claim 9 wherein said drive means includes upper and lower rollers in contact with said bars, means for adjustably positioning said rollers, and means driving at least one of said rollers.
14. The apparatus of claim 13 wherein said rollers 18. The apparatus of claim 9 wherein said tank is closed at its top by a hood connected to a fume removing means.
19. The apparatus of claim 12 wherein said recycle means includes a second tank of greater capacity than said plating tank and pump means for effecting said recycling, said plating tanks being arranged in said second tank so that fluid lost from said plating tank is retained by said second tank.
20. The apparatus of claim 9 wherein said first electrode comprises a copper electrode arranged around said bars and held in electrical contact therewith by clamping means peripherally of said bars.
21. The apparatus of claim 9 wherein said first electrode includes a hollow cylindrical body arranged coaxially with said bars and having seal means at the ends thereof, said seal means and said body forming a chamber, said chamber containing mercury and having a charged electrical connection in contact therewith whereby said connection and said mercury cooperate to charge said bars.