US3414503A - Apparatus for coating the surface of plates uniformly by cathode sputtering - Google Patents

Description

Dec. 3, 1968 E. BRICHARD 3,414,503

APPARATUS FOR COATING THE SURFACE OF PLATES UNIFORMLY BY CATHODE SPUTTERING Filed March 8, 1965 6 Sheets-Sheet 1 FIG. I

INVENTOR Edgurd Brichord ATTORNEY5.

Dec. 3, 1968 E. BRICHARD 3,414,503

APPARATUS FOR COATING THE SURFACE OF PLATES UNIFORMLY BY CATHODE SPUTTERING Filed March 8, 1965 6 Sheets-Sheet 2 FIG. 2

3' T I v 1 I I I l I 54L 37 +1 53 W35 35 i E g 3s 43 ,1 j E L g 36 ,jl

5s 49 L I6 2 6 I :1

INVENTOR Edgord Brichord BY W ATTORNEYS,

Dec. 3, 1968 E. BRICHARD 3,414,503

' APPARATUS FOR COATING THE SURFACE OF PLATES UNIFORMLY BY CATHODE SPUTTERING Filed March a, 1965 6 Sheets-Sheet s INVENTOR Edgclrd Brichurd FlG. 5 BY ATTORNEY 5.

Dec. 3, 1968 E. BRICHARD 3,414,503

APPARATUS FOR COATING THE SURFACE OF PLATES UNIFORMLY BY CATHODE SPUTTERING Filed March 8, 1965 6 Sheets-Sheet 4 INVENI'OR Edgcrd Brichord ATTORNEYS.

Dec. 3, 1968 E. BRICHARD 3,414,503

APPARATUS FOR COATING THE SURFACE OF PLATES UNIFORMLY BY CATHODE SPUTTERING Filed March 8, 1965 6 Sheets-Sheet 5 FIG. 9

- v S 59 T FIG. IO 38 M 79 INVENTOR O 3 26; Edgclrd Brlchurd ATTORNEYS.

Dec. 3, 1968 E. BRICHARD 3,414,503

APPARATUS FOR COATING THE SURFACE OF PLATES UNIFORMLY BY GATHODE SPUTTERING Filed March 8, 1965 6 Sheets-Sheet 6 FIG. I2

x I w 35 3| 30 37 as N 5 IO 5 37K. 5 INVENTOR 5| Edgurd Brichard ATTORNEY S.

United States Patent 45,647 12 Claims. (Cl. 204--298) ABSTRACT OF THE DISCLOSURE An apparatus for the coating of surfaces of large, fiat objects by cathodic volatilization of the coating material in a vacuum, the apparatus including means for holding the object in a plurality of vertical, parallel planes and at least one linear cathode electrode associated electrically 'with at least one anode electrode, the cathode electrode being provided with the coating material and extending parallel to the planes in which the objects are to be held, thelength of the cathode electrode extending entirely across the regions to be occupied by the objects, the apparatus further including means for moving the cathode electrode parallel to the planes in which the objects will be held in a direction transverse to the cathode electrode length and for a distance sufficient to cause the electrode to completely traverse the regions in which the objects are to be held.

The present invention refers to a process and apparatus for vacuum coating sheet materials, particularly glass sheets, by using the cathodic volatilization, or sputtering, process for volatilizing the coating material, said process consisting in moving at least one electrode to be volatilized in a direction parallel to the sheet to be coated. I

It is well known that the electrodes in such a process, whatever their number may be, must be placed near the surface to be coated if a uniform coat is sought as by applying the cathodic volatilization process to the coating material.

According to a known process, the sheets to be coated are placed horizontally in the same plane running through the upper part of an upright cylindrical tank. The electrodes to be volatilized are placed under said sheets between the vertical axis and the wall of the tank. As soon as a vacuum is produced in said tank and a voltage is applied to the electrodes, the sheets move around the vertical axis so that the surface which'is to be treated can pass one or several times before the electrodes.

The inside of the tank is then connected to the atmosphere so that the sheets can be removed from the tank and replaced by new ones.

This method involves serious inconveniences.

The total surface which can be coated in the course of one operation cannot exceed the surface of the tank section. Besides, the coatings made under those conditions are irregular. On one hand, the sheets placed in a horizontal position are supported along their edges and consequently sag so that their central part is nearer the electrode than are their margins. On the other hand, because the sheets are given a circular motion, the surfaces near the axis of rotation stay above the electrodes for a Patented Dec. 3, 1968 "ice longer time than do the surfaces located at a greater distance from said rotation center.

As the time of exposure of sheets placed at the same distance from the electrodes continuously varies and as these differences have to be compensated for, it has been suggested to shape these electrodes into sectors, so that the apex of the angle of these sectors coincides with the rotation center of said sheets.

Experience shows, however, that the coat obtained by utilizing such electrodes is thinner in the area near the rotation center, because the electrodes wear more rapidly at the apex of their angle.

The cathodic volatilization process can also be made use of for coating sheets by placing a plane or curved glass sheet horizontally in a tank whose interior pressure is below atmospheric and by having a volatilization electrode sweep one or more times past the lower surface of said glass sheet. If coats of different kinds have to be applied to said glass sheets, several electrodes, also of different kinds, have to be simultaneously displaced and separately made use of. The bottom part of the tank contains the mechanism for moving the electrodes, whatever their number may be, and must be such that the conduits connected to said electrodes, either for feeding them with an electrical current or for cooling them by means of a cooling fluid, can be moved horizontally. In both cases, the surface treated cannot exceed the cross section of the tan-k at the level of the sheet and the regularity of the coating is jeopardized by the fact that the sheet sags.

Further, it must be noted that none of the aforementioned devices can be used for simultaneously coating both faces of said sheets, if it is desired to do so.

The present invention has as a primary object the provision of a process for vacuum coating sheet materials by using the cathodic volatilization process for volatilizing the coating material, such a process consisting in simultaneously applying, to either one face or both faces of several sheets, coats of a very regular thickness with the result that the capacity of the coating equipment is considerably increased.

One can, for instance, coat in a cylindrical tank in the course of one operation a surface twenty times as great as the surface that could be coated according to known processes in a tank of a nearly equal diameter.

According to the process in conformance to the invention, one simultaneously coats the surfaces of a plurality of sheets by moving one or several electrodes of an appropriate shape between and along said surfaces, these surfaces being separated from each other and running in a direction nearly parallel to them.

The electrodes can be vertically placed between the pairs of sheets and moved horizontally between them, but preferably they are placed horizontally and moved vertically.

The invention also refers to a device developed for the practical application of this process in conformance to the invention, said device consisting of a tank connected to a vacuum source and supporting a plurality of sheets to be coated, at least one electrode placed in a parallel direction to the sheets to be coated, a mechanism for moving the electrodes in a direction parallel to said sheets and, finally, conduits for feeding the electrodes with an electrical current and cooling the same electrodes by means of a cooling fluid.

The device is conformance to the invention is characterized by the fact that said support is so shaped that it can maintain at least two sheets to be coated vertically opposite One another and that between both said sheets there is at least one electrode which is moved by said mechanism in a direction parallel to said sheets, all these mobile electrodes being simultaneously moved in the proper direction and advantageously operated by a single mechanism.

Preferably, the electrodes are placed horizontally and moved vertically.

As regards a particular modification of the invention, the electrodes are supported by a horizontal frame provided with tapped pieces run through by vertical screws which can be rotated successively clockwise and counterclockwise for raising and lowering the electrodes.

As regards another modification of the invention, the electrodes are supported by a horizontal frame guided between upright guides and alternatively driven upwardly and downwardly by chains.

A modification conforming to the invention has been so designed that the sheets can be easily placed in the tank and removed from it. Moreover, sheets of various sizes can be easily kept in position on their support.

With a view to easily placing the sheets in the tank and removing them from it when the cover of the tank is removed, the support of the sheets is provided with vertical guides for the removable frames supporting the sheets.

For keeping sheets of various sizes in position on these removable frames, the latter are provided with horizontal guides for intermediate uprights whose position is adjustable in the horizontal direction. Besides, each of these intermediate uprights serves as a vertical slideway for stops whose position is adjustable in height and maintains the sheets against the frame, attention being drawn to the fact that a part of the intermediate uprights belonging to a frame has its stops on one side of said frame and that the other part of said intermediate uprights has its stops on the other side of said frame.

As regards another modification of the invention, which has been so designed that each of the faces of the sheets are more easily coated, the frames are provided with upright guides for the horizontal intermediate crosspieces, whose position is adjustable in a vertical direction. The sheets are placed between these cross-pieces and kept in their position by means of U-shaped spring clamps and placed upon said cross-pieces in a straddling position, the ends of said spring clamps gripping the upper and lower edges of said sheets.

These and other objects and advantages of this invention will become more apparent upon reference to the following specification taken in connection with the accompanying drawings, in which:

FIGURE 1 is a plan sectional view of the device taken along the line II of FIGURE 2, just above the upright guides for the removable frames supporting the sheets to be covered;

FIGURE 2 is an elevation of the same device, which has been first cut along line I I-II of FIGURE 1;

FIGURE 3 is a side view of a removable frame drawn to a larger scale;

FIGURES 4 and 5 are vertical sections through the removable frame of FIGURE 3, these sections being obtained by cutting said device along lines =IV-IV and VV of FIGURE 3 and the same being drawn to a larger scale;

FIGURE 6 is a cross-section obtained by cutting the same device along line VIVI of FIGURE 4;

FIGURE 7 is a side view referring to another frame model;

FIGURE 8 is a vertical section through the ends of a pair of electrodes, supported by a double frame, this section being drawn to a larger scale;

FIGURE 9 is an electric wiring diagram of an installation for automatically reversing the direction of the rotary motion of the motor, vertically moving the electrodes, such automatic reversal occuring at each end of the stroke of said electrodes;

FIGURE 10 is a vertical section in another device used for vertically moving the electrodes in both opposite directions without reversing the direction of the rotary motion of the electric motor, used for this purpose;

FIGURE 11 is a section which is similar to the one shown on FIGURE 8. The two pairs of electrodes used can be used separately. Each pair is used for coating sheets with a material which is different from the one deposited by the other pair; and

FIGURES l2 and 13 show in a way similar to FIG- URE 2 two other devices designed in conformance to the present invention.

In these different figures, the same notations are used for designating identical pieces.

In the foregoing text as well as that following, the term electrodoe has been used without making any distinction between anode and cathode. In fact, the coating installations are generally fed with an alternating current and each electrode is thus alternatively anode and cathode.

The device shown on FIGURES 1 and 2 consists of a tank 1 with a vertical wall 2, a bottom 3 and a removable cover 4. The tank may be connected to a vacuum source, not shown, this by means of a piping 5 provided with a cock 6.

The suspension ring 7 with which the cover 4 is provided facilitates the latters placing and its being easily removed by means of a hoisting engine. There is an air seal 8 between said cover and the upper edge of wall 2 so that the necessary vacuum can be produced in said tank and maintained by means of cock 6.

The horizontal frames 9 and 10 are fixed to the ends of wall 2 by means of braces such as 11. These frames keep in position upright U-shaped slideways 12, which serve as guides for the removable frames 13 bearing the sheets to be coated, for example glass sheets to be covered with metal. These slideways have a bottom 12 on which the corresponding frame rests when it is in place.

The frames -13,one of which is shown in detail in FIG- URES 3 to 6, consist of two outer uprights 14 joined by an upper cross-piece 15 and a lower cross-piece 16. The upper cross-piece 15 is provided with suspension rings 17. Near the upper and lower cross-pieces, the outer uprights 14 are joined by means of horizontal guides for intermediate uprights 18, of which the position is adjustable in a horizontal direction.

Some of these intermediate uprights have not been shown in order to simplify FIGURE 3. The upper horizontal guide is made up of two flat iron pieces 19 and the lower horizontal guide by two flat iron pieces 20.

Each of the intermediate uprights is made of a tube having a square cross section and laterally provided with a vertical slot 21 traversed by screws 22 used for blocking slides 23 whose position is adjustable in height. These screws are provided with stops 24 used for holding the sheets to be coated against the frame. One of these sheets is shown on FIGURE 3, in which it is designated by 25. Some of the intermediate uprights of each frame have their vertical slot 21 on one side of the frame considered and the others on the opposite one. The stops, of which the position is adjustable in height and which are to be found on one side of the frame, can consequently be used for keeping the sheets in position on this side, whereas the stops on the opposite side are used for keeping the sheets in position on their side.

It is to be noted that as a consequence of the independent adjustment of the position of the stops located on different intermediate uprights, the frame can be used for supporting sheets of different sizes on either face of the sheet.

A plate 26 (FIGURES 3, 5) sufliciently wide to bear against one of the edges of each of the fiat iron pieces as well as a tapped plate 27 placed between the flat iron pieces 19, are attached to each intermediate upright 18. This last plate acts as a nut in regard to bolt 28 which by being screwed into this nut presses the plate 29 against an edge of the flat iron pieces 19. By screwing into nut 27 the bolt 28, whose head rests upon plate 29 supported by two flat iron pieces 19, the tube 21 can be raised until the plate 26 fixed to the lower end of said tube meets the lower edges of the flat iron pieces 20. At this moment, the intermediate upright is fixed in position as far as the flat iron pieces 19 and 20 are concerned. It is in this position that the intermediate uprights 18 hearing the glass sheet have been drawn in FIGURE 3.

FIGURE 3 shows that each intermediate upright 18 is provided with two pairs of stops 24. Each upright of this kind can thus support two or three sheets placed one above the other against a face of the frame. Each intermediate upright could obviously be provided with a greater number of stops.

In order to simplify FIGURES 1 and 2, glass sheets 25 are only shown placed against the faces of a single removable frame 13. It is understood that all the frames can bear glass sheets to be coated.

These frames are particularly suitable when one face of each sheet is to be coated.

If both faces of a sheet are to be coated, one preferably uses, for instances, a frame similar to that shown as an alternative in FIGURE 7.

This latter frame is provided with upright guides each made of two flat iron pieces 83-84 fixed opposite each other at the ends of cross-pieces 15 and 16, such upright guides being provided with longitudinal slots 85. Crosspieces 86 which can slide between said flat iron pieces 83- 84 bear at their ends set screws 87 guided by the slots 85, which set screws can be used for adjusting said crosspieces in height and for securing them at the selected height. The glass sheets 25 are placed between these crosspieces and kept in position by means of spring clamps 88 the ends of which grip the edges of said glass sheets.

The device designed in conformance to the invention aims at vacuum coating the different sheets by using the cathodic volatilization process for volatilizing the coating material. To this purpose, it is made up of electrodes placed horizontally in a direction parallel to the sheets borne by the removable frames between which the electrode considered is placed. Each electrode is thus used for simultaneously coating a pair of sheets between which it is placed, said pair of sheets being borne by adjacent frames.

In a model of the invention, designed as shown on FIGURES 1, 2 and 8, the electrodes 30 and 32 are placed one above the other and fixed to frames 31 and 33, respectively, which are similar in shape to the horizontal frames 9 and 10, between which they can be vertically moved. The frames 31 and 33 are connected to each other by braces 34 (FIGURES 1 and 2) which are at the same time used for supporting tapped pieces 35 which are traversed by vertical screws 36. These screws can be rotated successively in opposite directions, namely clockwise and counterclockwise, for alternately raising and lowering the electrodes 30 and 32. Said screws 36 are vertically maintained in the bearings 37 between which the tapped pieces 35 can be moved.

The extreme positions of the frames 31 and 33, and consequently those of the electrodes 30 and 32, are to be found beyond the upper and lower levels of the sheets to be coated, because experience has shown that this is necessary in order for the coating to be uniform. The frames 9 and 10, on which the upright guides 12 are mounted, must be placed respectively above and below the extreme positions of the frames 31 and 33 so that the electrodes 30 and 32 can move freely.

.These electrodes are made of tubes through which a cooling fluid circulates. For this purpose, their ends are connected to tubes such as 37 (FIGURE 8) by means of electrical insulating sleeves 38. Tubes 37, which convey said cooling fluid into the tubular electrodes, are connected to a distributing box such as 39 (FIGURE 2) fed with cooling fluid by means of a pipe 40 ending outside the tank 1. Tubes similar to tubes 37 are connected to the opposite end of electrodes 30 and 32 with a view to discharging the cooling fluid into another distributing box 41 connected to the outside of tank 1 by means of a tube 42. In order to simplify FIGURE 2, the tubes between the distributing boxes 39 and 41 and the electrodes 30 and 32 have not been drawn.

FIGURE 8 also shows the electric conductors 43 and 44 connected to electrodes 30 and 32, respectively, which conductors convey electrical current at the voltage necessary for vacuum coating the sheets by using the cathodic volatilization process for volatilizing the coating material. The conductors 43 and 44 of the different pairs of electrodes end at a distributor 45 (FIGURE 2) connected by means of a cable 46 to a current generator, which is not represented in the drawing.

Only one pair of the conductors 43 and 44 has been represented in FIGURE 2.

A reversible electric motor 47, powering a speedreducer 48, simultaneously rotates all of the vertical screws 36, as shown in FIGURES 1 and 2. A sprocket 49 meshing with an endless chain 50 passing over sprock-- ets 51 keyed to the vertical screws 36 is keyed to the output shaft of said speed reducer. Said chain 50 is supported between the sprocket-s 51 by means of a platform 52 on which it slides.

Preferably, the direction of the rotary motion of the electric motor 47 is automatically changed as soon as the electrodes 30 and 32 have reached a level which exceeds the upper or lower level to which the sheets supported by the removable frames 13 can extend. For this purpose, use can be made of an electric circuit which, as shown in FIGURE 2, is provided with a limit switch 53 which limits the up stroke, a limit switch 54 which controls the down stroke, a limit switch 55which limits the down stroke and a limit switch 56 which controls the up stroke, such limit switches being inserted in electrical circuits of the type shown in FIGURE 9. Said switches 53 and 55 are normally closed, whereas the switches 54 and 56 are normally open.

The electric motor 47 is a three-phase motor which is connected to three electric conductors 57, 58 and 59 from which the necessary electric power is taken. These conductors can be respectively connected to the conductors R, S and T of the three phase system by closing a triple pole switch 60 controlled by a relay coil 61 or respectively to conductors R, T, S by closing another triple pole switch 62, controlled by a relay coil 63.

These two triple pole switches are normally opened and are closed only when the coil of the corresponding relay is traversed by a current. This current is generated by a current generator schematically shown by a storage battery 64, to which the conductors 65 and 66 are connected.

The conductor 65 is connected to coil 61 and the latter to a push-button switch 67 which is itself connected in series with a hand-operated switch 68 which is normally closed. This last switch is connected to conductor 66.

The conductor 65 is also connected to coil 63 and the latter to a push-button switch 69, which is itself connected in series with a hand-operated switch 70 which is normally closed. This last switch is connected to conductor 66.

When the push-button 67 is momentarily closed, the current passes through the relay coil 61 and closes the triple pole switch 60 and a holding in position, contact 71 inserted in series with the limit switch 53 for limiting the up-stroke, these being in shunt with a circuit in which the push-button 67 and the hand-operated switch 68 are inserted. Switch 53 is normally closed. One can, thus, immediately let the push-button 67 snap back into its open position without deactivating coil 61, so that the motor 47 continues to be fed by the conductors 57, 58 and 59 with the electric power taken from the power system by means of conductors R, S, T. If it is assumed that the frames 31 and 33 are in a position corresponding to the lower end of the screws 36, that is to say at the end of their down-stroke, and that the direction of the rotary motion of the electric motor 47, fed with an electric current as described above, is the direction for which said frames 31 and 33 are raised by the aforementioned screws 36, it is easy to understand that, owing to the fact that these frames are being raised, when the frames near the top of their travel path, the limit switch 53 limiting the up-stroke will open a little time before the switch '54 initiating the down-stroke closes. As soon as the switch 53 opens, the current flowing through the relay coil 61 is switched off and consequently the motor 47 receives no more electric energy from the power system.

At almost the same time, when the switch 54 closes the relay coil 63 is supplied with current. As soon as the triple pole switch 62 is closed, the conductors 57, 58 and 59 are connected to those designated by the letters R, T and S and are thus connected to the power system. Consequently the electric motor rotates in a direction which is opposite to the direction in which it rotated when the tripple pole switch 60 was closed.

The triple pole switch 62 closes simultaneously with a holding in position contact 72 which is the same as contact 71 but which acts when switch 54 closes or when the push-button 69 temporarily closes for initially starting motor 47 so as to cause it to rotate in a direction which causes the frames 31 and 33 to be lowered.

The downward motion of frames 31 and 33 continues until said frames meet the limit switches 55 and 56. As soon as the switch 55 opens, the coil 63 is no longer traversed by an electrical current and consequently switch 62 opens and the electric motor 47 is no longer fed with the electric power taken from the power system. Shortly thereafter, the switch 56 closes and consequently the coil of contactor 61 is again traversed by an electric current which causes the motor to rotate in the direction for which said frames 31 and 33 move upwardly.

It can thus be seen that the electrodes 30 and 32 automatically move upwardly and downwardly whereas they remain parallel to the sheets between which they are placed.

This automatic reciprocating motion continues until one of the hand-operated switches 68 or 70 is opened. In fact, when one of the latter is opened, it nullifies the effect of its corresponding control limit switch when this last switch is automatically closed, which closing would normally have caused the direction in which motor 47 was rotating to be reversed.

FIGURE shows an alternative device according to the invention in which the motor used for moving the electrodes in a direction parallel to the sheets to be coated can be rotated in but one direction until the coating operation is achieved. The frames 31 and 33, joined by braces 34, are moved by means of a slideway 73 which is integral with them and in which a pin 74, borne by a chain 75, slides. This chain passes around sprockets 76 and 77 of which one is constantly rotated in the same direction by a motor 47 and a speed reducer provided, for an example, with a belt 78 passing around pulleys 79 and 80 of respectively different diameters. The slideway 73 is held in a vertical guide 81 in which it can slide, said guide being fixed to the cylindrical wall 2 by means of braces 82.

FIGURE 11 shows another alternative device in conformance to the invention in which two pairs of electrodes 30 and 32 and 30' and 32 which can be simultaneously moved are placed between the opposite faces of the sheets 25 to be coated, one pair of electrodes being used for coating sheets with a coating material different from the one deposited by the second pair of electrodes. The electrodes 30 and 32 will be used, for an example, for coating the sheets with copper, whereas the electrodes 30 and 32' can be used for coating sheets with alumina or bismuth oxide. These coatings are applied successively by electrically connecting the electrodes at different moments, the electrodes 30 and 32 being supplied with energy by means of conductors 43 and 44 and the electrodes 30' and 32 being supplied by means of the conductors 43' and 44'.

As regards the device shown in FIGURE 12, only the electrodes 30, which are really cathodes, can be moved in a direction parallel to the sheets 25 to be coated. An anode 32 common to all the cathodes is placed against the bottom 3 of the tank 1. A great number of elements can be placed inside this tank but have not been represented on the drawing because the drawing would have become unintelligible without this intentional omission. This is also the reason why only a small number of frames used for supporting the sheets have been drawn. The whole of the apparatus could also be used as an anode of the type designated by number 32".

FIGURE 13 shows another device which conforms to the invention and in which one single electrode is placed in each space between the sheets supported by two adjacent frames. In this case, a pair of electrodes is made up of two neighboring electrodes, that is to say that every other electrode is connected to be at one voltage polarity and the intervening electrodes are connected to be at the opposite voltage polarity.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions; and accordingly, it is desired to comprehend such modifications within this invention as-may fall within the scope of the appended claims.

I claim:

1. An apparatus for coating the surfaces of large, fiat objects by cathodic volatilization of the coating material in a vacuum, comprising, in combination:

a tank adapted to have its interior placed under a vacuum;

holding means disposed in said tank for holding such objects in at least one of a plurality of vertical, parallel planes, each such plane representing an object-holding region;

electrode means disposed in said tank and including at least one linear cathode electrode associated electrically with at least one anode electrode, said cathode electrode including the coating material and extending parallel to such planes, each said cathode electrode being disposed between two such planes and having its length extend entirely across one dimension of the object-holding regions between which it is disposed;

electrical means connected for energizing said at least one cathode electrode; and

movement producing means operatively associated with said electrode means for moving said at least one cathode electrode parallel to such planes in a direction transverse to its length and for a distance sufiicient to cause said cathode electrode to completely traverse the object-holding regions between which it is disposed.

2. An apparatus as defined in claim 1 wherein said movement producing means comprise frame means supportingly engaging said electrode means, and vertical screws in said tank threadedly engaging said frame means and rotatable for moving said frame means and said electrode means carried thereby in the vertical direction.

3. An apparatus as defined in claim 1 wherein said movement producing means comprise frame means in said tank supportingly engaging said electrode means, and chains in said tank connected with said frame means for moving said frame means vertically in said tank, said tank including vertical guide means-therein guidingly engaging said frame means.

4. An apparatus as defined in claim 3 wherein said guide means are in the form of vertically extending U-shaped slideways fixed in said tank.

5. An apparatus as defined in claim 4 further comprising frames provided in said tank and connected, on the one hand, to said tank and, on the other hand, to said slideways to support said slideways in said tank, said frames being located in said tank beyond the limits of the movement experienced by said frame means supporting said electrode means.

6. An apparatus as defined in claim 1 wherein said holding means for supporting such objects in said tank include frame members which are removable from said tank.

7. An apparatus as defined in claim 6 wherein said removable frame members include horizontal guides; uprights adjustably positioned in said guides; and supporting stops carried by said uprights and adjustable therealong for supporting engagement with the edge portions of objects of varying sizes to be coated.

8. An arrangement as defined in claim 9 wherein each of said uprights is slotted in the vertical direction, and said holding means further comprise a plurality of blocks in each of said uprights and a plurality of screw threaded clamping means each connected with a respective one of said blocks and extending through the slot of its associated upright for adjustment of said blocks and clamping means vertically along the uprights, and stop means carried by said screw threaded clamping means externally of said uprights for engagement with the edges of objects to be supported in said tank.

9. An arrangement as defined in claim 1 wherein said holding means comprise: a plurality of vertically spaced horizontal guides; a plurality of end uprights extending between said horizontal guides near the ends thereof; a plurality of intermediate uprights extending between said each said intermediate upright having means for abutting beneath the bottom of the lowermost one of said horizontal guides; and screw threaded engagement means carried by the upper end of each of said intermediate uprights and extending through the uppermost one of said horizontal guides for adjustably clamping its associated intermediate upright to said uppermost horizontal guide.

10. An arrangement as defined in claim 1 wherein said holding means comprise: an upper and a lower horizontal member; two laterally spaced uprights extending between, and connected to, said horizontal members near the ends thereof, each of said uprights being vertically slotted; a plurality of intermediate horizontal members extending between said upright members; and connecting means attached to said intermediate horizontal members and extending through the slots in said upright members for adjustably securing said intermediate horizontal members along said upright members.

11. An arrangement as defined in claim 1 further comprising means associated with said electrode means for supplying cooling fluid thereto.

12. An arrangement as defined in claim 1 wherein the objects to be coated are constituted by substantially flat glass sheets.

References Cited UNITED STATES PATENTS 2,043,966 6/ 1936 Whiston et al 204-298 2,435,997 2/1948 Bennett W 118-49 2,703,549 3/ 1955 Ransburg 118-51 2,716,622 8/1955 Foster 117-201 2,736,671 2/1956 Ransburg et a1. 117-93 2,754,227 7/1956 Ransburg 117-93 2,801,607 8/1957 Vodar et a1 118-491 2,886,502 5/1959 Holland 204-192 3,293,168 12/1966 Schulz 204--192 3,294,670 12/1966 Charschan et al. 204-192 FOREIGN PATENTS 345,662 5/ 1960 Switzerland. 706,003 3/1954 Great Britain.

ROBERT K. MIHALEK, Primary Examiner.

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