BAND-PLATING APPARATUS

Abstract: Bandplating apparatus, where any flexible synthetic bands or synthetic-coated and endless screening metal bands are arranged by their surfaces fitting to each other, moving on sides of the metal plate to be plated at synchronized speed. The endless screening bands move on guiding and conveyor discs which have fixed and adjustable shafts, the band being tensioned sufficiently for the drive. Two screening bands are mounted on the plating side of the metal band spaced from each other according to the strip width, tensioned independently from each other with three adjustable tensioning discs, thereby realizing the unilateral strip plating. A screening band with its surface fitting to the metal band moves on the plating side of the metal band, said screening band is provided with line of guide-holes and with openings corresponding to the spots to be plated. During the movement of the metal band to be plated and the screening band, the lines of guide-holes formed on them constantly cover each other, thereby realizing the unilateral spot plating.

Description: BAND-PLATING APPARATUS The electric or electronic apparatuses have an ever increasing role in the technical development of our age in the field of instrument technique, telecommunica¬ tion and automation. Meeting the requirements of reliability is the most vital problem in the instrument technique, telecommunication and automation, since regulation, control and supervision of very expensive technological or other apparatuses are entrusted to the electric or electronic devices, the breakdown of which would adversely influence the productive work both in a smaller or larger comrainity, not to speak about mass jeopardy. A large number of standard and special com¬ ponents are built into the electric and electronic apparatuses, the breakdown possibilities of which are very diverse. The experiences prove that most of the break¬ downs occur at the electro-mechanical parts, partly as breakage arising from fatigue of certain mobile parts, and partly from inadmissible corrosion of the contacts. In case of electronic apparatuses operating with low signal levels (mV, .uV, mA), breakdown due to corrosion may frequently occur, since these apparatuses operate under the most difficult climatic conditions in many cases. The contact resistivity of the contacts of electromechanical parts operating in highly corrosive medium may change to such extent, that they become useless. Naturally similarly to the corrosive effects, the breakdowns may be caused by other conditions as well. Wear of the surfaces in contact is significant among the causes of breakdown in apparatuses operating similarly with low signal levels. This phenomenon occurs in the elctromechanical parts of the frequently used apparatuses. In the production of the up-to-date electro¬ mechanical parts, the various precious metal layers appli on the contacting surfaces are qualified for preventing the breakdowns arising from corrosion and wear. Mainly copper is used as the basic material of cantacts, for its excellent suitability to carry out the current-conduction function. In order to improve the properties, the copper is generally used in various alloys. With the alloying elements to the copper, first of all the various mechanic properties can be.altered. OM Increased hardness, tensile strength, elonga¬ tion, etc. can be attained with the various bronze alloys, produced in the form of plate, band and rod (sometimes casting)• A certain part of the electric contacts performs springy function, in order to bring about contact pressure of adequate extent. Regarding their shape they can be produced by milling and metal pressing. Silver (Ag), palladium (Pd), rhodium (Rd), gold (Au), and platinum (Pt) are generally used for precious metal coating of the electric contacts produced all over the world. The properties (chemical, mechanical, electic, etCo) of these precious metals show significant deviation from each other. Meeting and increasing the reliability require¬ ment of the contact systems justify the increased use of the precious metals, but on the other hand the ever increasing prices of the world market are against it« The first part of the solution - the principle of applying the precious metal only on the contacting surfaces - was laid down several years ago, but economical technique at acceptable level in a wide range is not available even today. Previously the total surface of the contacts produced by metal pressing and milling were plated with precious metal, suspended, or mass produced in drum or bell. - * ξTCf " i- 7 O PI Such precious metal plating baths were deve¬ loped for the process, with which the contacts were co¬ ated at a high rate of productivity. The situation became untenable with the fast increase in the prices of the precious metals. Some of the experts started to reduce the layer thickness at the expense of the qualiry and reliability, while others started the development of more wear-resistant and anticorrosive plating baths and coatings, in order that the technical value of these thinner precious metal layers applied on with these baths should remain the same as that of the earlier thicker layer. The situation was significantly changed when the partial (selective) plating of the contacts with • precious metal was commenced. Complete plating on one side of the band material of the contacts, or plating in several strips was relatively quickly solved (hot rolling of basic material and precious metal). However with the plating process it was possible to roll only relatively thick precious metal strips (precious metal thickness/ basic material thick¬ ness minimum 10 %)• The application of thinner precious metal layers with partial process commenced only later. They started out in two ways: first with the partial dipping of the contacts in the precious me¬ tal plating bath, then later with plating the copper, or copper alloy band material of the contact fully on one side, or in strips on both sides. With these two methods the use of precious metal was succesfully and significantly reduced, since frequently 10-12-times reduction was reached. Besides the significant reduction of the precious metal utilization, both methods have their drawbacks, and further possibilities. At the various contacts in most of the cases it is sufficient to apply the precious metal to one side of the contact, since the contacting surface (generally line or spot) is only on one side. Thus by dipping the raw contacts pressed from the band in the precious metal plating bath involves in most cases the use of excess precious metal. In case of the copper, or copper-alloyed band materials plated continuously on one or both sides with precious metal strip, the precious metal application is already "controlled * ', but the pressing wastage with precious metal content is a disadvantage (wastage in step between the two contacts)<_ Naturally the precious metal content of the pressing wastage can be recovered, but losses occur in any case in the form of the used chemicals and in the efficiency of the precious metal recovery. The so-called spot plating of the bands with precious metal is a suitable technological method for the final elimination of the precious metal losses arising as described above. In this case the surface (spot) to be plated with precious metal is worked out not only in cross direction but also in longitudinal direction of the band, thus the economic efficiency can be increased to the maximum possible. For spot plating of the bands it is necessary their preparation, prepressing with line of guideholes, since this forms the position basis of the selected spot plating, furthermore the following contact pressing. In respect of the pressing technology, the pressing of the line of guide-holes represents extra operation, but this input is negligible compared to the attainable saving of the precious metal. The opera- tion is rationally carried out on quick-pressing machine by pressing about 4-10 holes at a time. For selection of the punch and feeding device the +_ 0.005 mm hole spacing or stepping accuracy is decisive. Apart from the pressing-in the line of guide holes, further possibility is the pressing in advance of the so-called wastage between the consecutive contact (in one process with pressing the line of guide-holes). In case of prepressed band the metal layer is to be applied always on the side free from burr. By suitable screening of the prepressed band in the latter case precious metal can be applied not only on the working surface of the direct contact, but - first of all for corrosion reasons - it is applicable also on the small surface cut perpendi¬ cularly to it. Its advantage is, that the traces of possible corrosion can be kept away from the working surface. At continuous strip plating of the bands, the band parts not to be plated with precious metal are led along the whole length of the bath between adjustable screening plates produced from nonconductive materJaL (syntherics not detrimental to the precious metal baths, such as PVC, polypropylene, etc.). Plane of the band surface in the bath may be: horizontal and vertical. At spot plating of the bands, the band parts not to be plated with precious metal are coated with lacquers not detrimental to the precious metal baths, which screening material is removed with chemical and mechanical means after the plating. The lacquer for screening is applied on th e band with rolls by sprinting technical method, after the described prepressing, proper cleaning, washing and drying of the surfaces. The screening to be printed on the band is applied on the mantle of the pressing rolls naturally with consideration to the line of guide-holes as spacin and positioning basis. Diameter of the pressing rolls is selected as to be able to apply whole divisions around the mantle (roll diameter is about 80 - 120 mm). Quality (consistency) of the lacquer materia is selected as to attain about 0.1 mm edge accoracy at the limit of the lacquered and unlacquered surfaces. Impression of the lacquer is continuous and after the process it is dried at about 140 - 160°C temperature for 20 - 25 seconds by pulling through an electric drying oven at continuous rate, then it is wound up for plating. The plating in this case is carried out by pulling through the band in its horizontal position without bending. Thickness of the metal and precious metal layers is influenced by the parameters of the applied p3εting bath, length of the plating tubs and the rate of pulling through the band. Thus the contact production consists of fou independent processes: Prepressing Screening by impression of the lacquer Selective plating, screening with removal Contact pressing. The described band screening and selective band plating apparatuses, as well as the related technology generally fulfil the technical-economic requirements related to the use of precious metals in respect of both the qualitive and reduced quantitative utilization. However the contact production consisting of four technological processes have certain problems, e.g. screening device produced at significant cost, and the extremely strict parameters at the lower productivity of the related technology, which altogether in the final analysis increase the production cost. The band plating apparatus according to the invention performs the mechanical screening of any surface of the band in a relatively simple way. The apparatus according to the invention is described wxth the aid of the enclosed drawing by way of a preferably embodiment, as follows: Figure 1/a: Overflow plating bath circulating apparatus, Figure 1/b: Top view of Figure 1/a, Figure 1/c: Side view of Figure 1/a, partly sectional view, Figure 2: View of metal band. Figure 3: Top view of band plating apparatus, Figure 4: View "A" of Figure 3., • Figures 5/a,b,c: Band formations. Figure 6: Selective plating apparatus, Figure 7: View "A" of Figure 6, Figures 8/a,b,9,10: Band guiding device, Figure 12: Completely assembled apparatus. The plating is carried out in the "overflow plating bath circulating apparatus" according to Figures 1/a r 1/c, in vertical position of the band surface. The build-up of the apparatus is suitable for lifting the level of the plating bath to variable height. Fine adjustment of the bath level 8 is accomp¬ lished with the aid of two adjustable regulating slides 11 mounted above the overflow edge at the two ends of the plating tank 1. The apparatus is mounted with its base plate onto a horizontal table top 12, below which a synthetic tub suitable- for receiving the plating bath is arranged with the necessary filtering, heating and circulating pump system. Length of the apparatus is determined by the exposition parameters of the plating bath, the necessary maximum layer thickness and by the speed of band conveya The plating and the similarly built economy- flushing and flushing apparatuses are arranged paralϋe 1 with the longitudinal axis one after the other in accord with the technological sequence ii such a way, that the band with vertical surface can be pulled through in a straight line along the centreline of the apparatuses. The band is pulled through with driving gear driven rolls, the speed of which is adjustable with interchangeable gears 20. 5 Should the set band pulling speed result in greater layer thickness at one of the plating apparatuses or baths within the technological sequence, while it is the required value at another one, it is possible - at identical band speed and under the same current condi- 10 tions - to reduce the layer thickness (clearly shown in the drawing) by replacing the plating tank with a shorter one within a few seconds. The new band plating apparatus mechanically screens the. band surfaces at the required places in 15 such a way, that the screening band moves together with .the plating band at the same rate. These screening bands for strip and spot plating are shown in Figures 5a - 5c. With the aid of the band screening devices 0 the band surface(s) to be plated will be continuously screened on one or both sides until the band moves in the plating tank. The screening bands made suitably of synthe- tis material or thin metal coated with synthetic material 25 are mounted - after blind splicing - in such a way, that the spacing of the line of guideholes pressed on at spot plating and spacing of the plating spots should be of whole PI size at the blind splicing. Suitable quality and thickness of the screen¬ ing bands are.the following: At strip plating: Hard P C band in 0.3 - 0.4 mm thickness, or hard bronze band in 0.15 - 0.2 mm thickness coated with 60 - 80 Aim thick synthetic material. At spot plating: 0J5 - 0.2 mm thick hard bronze band coated with 60 - 80 .urn thick synthetic material. (Alternative material: Anticorrosive semi- hard steel band in 0.15 - 0.2 mm thickness.) Vital properties of the 60 - 80 ,um thick synthetic coating: - wear resistance - effective adhesive power to the screening metal band - neutral reaction on precious metal plating baths (and other e.g. Sn plating baths as well) - effective electrical insulation - smooth surface (max. 15 Ai roughness) - resistance against acidic and alkaline re¬ action (3 pH - 12 pH) - temperature resistance to 90°C. Polytetrafluorethylene is one of the best synthetic materials that meets above requirements, but there are synthetics which are also effectively applicabl on the metal band, e.g. with electrostatic dusting follow s O with burning-in. The spacing accuracy of the pressing for screening bands 16, 17 - similarly to the spacing accuracy of the line of guide-holes for the spot plating bands - is generally + , 0.005 mm, hence it is suitable to punch the line of guide-holes with the same tool naturally complemented with the cutout of the spot(s) to be plated (by use of interchangeable stamp in the prepunchnig tool). The figure shows the plain and pinned discs driving the bands to be plated and the screening bands. At spot plating the band drive with pinned disc ensures the synchronous running of the band and screening bands, furthermore the identical height in vertical direction. As the total effect of these factors a precious metal spot positioning tolerance is given on the metal band which is satisfactory if +_ 0.10 - 0.2 mm in both directions. In order to increase the plating position accuracy, the screening bands on the band screening devices can be tensioned as shown in the drawing (with mobile tensioning rollers). By tensioning the screening bands, the pro- per synchronous running of the band surfaces can also be ensured. For the safe synchronized running of the bands - without gap - a band guiding device is available / OMPI /.<- WHO (and can be mounted within a very short time, as necessary) as shown in Figures 8 - 9 - 10. The apparatus is adjustably arranged on two brackets in the longitudinal axis of the plating appara Fixed and spring-loaded 33 tensioning rollers 35 are arranged on the main support 30 of the apparatus at suitably selected distances, which prevent the lateral displacement of the synchronous running band surfaces a this way no excess precious metal is applied on the ban At strip and spot plating of the bands in most cases the precious metal is applied only on one side of the band, hence the rear side of the bands has to be completely screened. The so-called "rear" screeni band is mostly a plain non-perforated synthetic materia or metal band coated with synthetic material. As shown in the figures this "rear" screenin band can be separated from the metal band -. after runni out of the bath - and can be guided back already earlie than the one on the front side. This way the cathode current can be conduct onto the band with the aid of the plain metal disc oppos the pinned conveyor disc. The figures show the band conveyor driving gear with the aid of which - through interchangeable gears - the speed of the band is variable. Synchroniza¬ tion of the speed of the screening bands and metal band is attained with further gears with the same tooth O number - participating in the drive - and with chain wheels (similarly with the same tooth number). The band plating apparatus and related band screening device described in the foregoing are not the only possibilities for solving the task. A band plating apparatus was worked out - as shown in Figure 11 - with the related band screening device. Principle of the solution is similar to the one applied at the above described band screening device with the difference, that the metal band to be plated moves with horizontal surface in the plating bath to¬ gether with the screening bands. The band movement from one bath into the next one is aided with guide rollers arranged between the tubs, while tensioning of the screening bands is ensured with tensioning rollers arranged on separately moving carriages• In order to attain favourable bath flow, the plating tubs have small volume, the baths are delivered with separate pump system from the large sized tanks arranged separately. (Naturally through the necessary filtering and heating devices.) The band movement - at variable speeds - is carried out with the driving gear arranged after the plating tubs assembled according to the sequence of the operation. It is unnecessary to describe here the further structural solutions of the selective band plating apparatuses, because their details are already widely known (e.g. winding on and off the band, apparatuses, devices adjusting regulating the plating process, etc.)

Claims: WHAT WE CLAIM IS 1. Band plating apparatus, c h a r a c t e r i z ¬ e d in that flexible synthetic bands or synthetic-coated and endless screening metal bands are arranged by their surfaces fitting to each other, moving on sides of the metal plate to be plated at synchronized speed. 2. Apparatus as claimed in claim 1, c h a r a c ¬ t e r i z e d in that the endless -screening bands move on guiding and conveyor discs which have fixed and adjustable shafts, the band being tensioned sufficiently for the * drive. O 3. Apparatus as claimed in claim 1, c h a r a c ¬ t e r i z e d in that two screening bands are mounted on the plating side of the metal band spaced from each other according to the strip width, tensioned independent¬ ly from each other with three adjustable tensioning discs, 5 thereby realizing the unilateral strip plating. 4. Apparatus as claimed in claim 1., c h a r a c ¬ t e r i z e d in that a screening band with its surface fitting to the metal band moves on the p ' lating side of the metal band, said screening band is provided with line of guide-holes and with openings corresponding to the spots to be plated. During the movement of the metal band to be plated and the screening band, the lines of guide-holes formed on them constantly cover each other, therdy realizing the unilateral spot plating. 5. Apparatus as claimed in claim 1., c h a r a c ¬ t e r i z e d in that a non-perforated screening band - with its surface fitting to the metal band and tension ed with two adjustable tensioning discs - moves on the non-plated (rear) side of the metal band. 6. Guiding and conveyor discs with fixed and adjustable shafts as claimed in claim 2«, c h a r a c ¬ t e r i z e d in that the shafts are positioned vertica or horizontally. 7. Guiding and conveyor discs as claimed in claim 2., c h a r a c t e r i z e d in that the mantle surface of these discs for strip plating are plain, while the conveyor discs for spot plating have pinned mantle surface formed to suit the spacing of the lines of guide¬ holes and the hole diameter of the metal and screening bands. 8. Apparatus as claimed in claim 1., c h a r a t e r i z e d in that the plain and pinned conveyor dis are connected through chain to a drive with interchangeab gears. 9. Plain or pinned conveyor disca as claimed in claim 7., c h a r a c t e r i z e d in that supporti discs are arranged opposite said discs having parallel sh and identical diameter, said supporting discs surround th metal band. 10. Band plating apparatus as claimed in claim I., c h a r a c t e r i z e d in that a "band guiding device" is adjustably arranged above the plating bath along the longitudinal axis of the metal band that has - mTBi OM vertical surface, on which fixed and spring-loaded rollers with parallel shafts are arranged in pairs. /

Inventors: ANGYAL I
Applicants: KONTAKTA A
Application year: 1981
Main classification: C25D5
IPC codes: C25D5, C25D7