Coating Apparatus

Abstract

Capacitors are transferred one at a time by a vacuum feed chuck to one of a plurality of vacuum mounting heads which are moving along a definite path. As the capacitors are conveyed along the path, and exposed portion thereof to be coated is submerged to a prescribed depth in a liquid coating material. Next the vacuum mounting head is rotated to expose a further portion of the item to be coated in operating orientation, after which this portion then receives a coating as before. The freshly coated part is then passed through a lehr where the coating material is heat hardened. Finally, the capacitor is contacted by an arm as the vacuum head carrying it moves along the path, thereby disengaging it from the head and allowing it to drop into a receptacle.

Description

The present invention relates generally to electrically conductive coatings, and, more particularly, to the provision of such coatings on electrical and electronic devices to serve as connective electrodes.

Along with the ever increasing tendency towards reduction in size of electronic circuits and circuit components, a concomitant problem has been the provision of conductive electrodes on such circuits or components by which they may be connected to other circuits or apparatus. That is, although the individual items to which the electrodes are applied are relatively small, requiring the electrodes to be commensurately small, such electrodes still must be of sufficient size and rugged enough to permit adherence thereto of, say, a wire or other lead element. In addition to being strong enough to support final connection in a circuit with other apparatus, it is conventional to subject the circuit or component to one or more testing operations which require disturbing the electrode with a temporary connection for each such test.

In the past, for example in the fabrication of small sized capacitors, final connecting electrodes have conventionally been applied by hand dipping or hand painting of a conductive liquid onto prescribed areas of the capacitor which, after drying and heat curing, sets up to provide a finished electrode. Hand dipping or hand application of electrodic coatings have not been completely satisfactory for a number of reasons. First of all, hand coatings are very difficult to apply uniformly over precisely defined small areas. Also, it is highly advisable that the thickness of such coatings be maintained uniform in order not to induce a spurious electrical resistance factor and this is difficult to obtain in a hand operation. Still further, coating materials have not infrequently been accidentally applied to other regions of the capacitor during hand painting, which might give occasion for an electrical short. Lastly, and perhaps most important, hand application of electrodes adds a considerable labor cost to the overall manufacturing expense.

SUMMARY OF THE INVENTION

In the practice of the present invention, a plurality of capacitors to be provided with coated electrodes are arranged seriatim by a vibrator feeder and with uniform orientation. The capacitors are transferred one at a time by a vacuum feed chuck to one of a plurality of vacuum mounting heads forming a conveyor which moves along a definite path. As the capacitors are conveyed along the path, an exposed portion thereof to be coated is submerged to a prescribed depth in a liquid coating material. Next the vacuum mounting head is rotated to expose a further portion of the item to be coated in operating orientation, after which this portion then receives coating as before. The freshly coated part is then passed through a lehr where the coating material is heat hardened. Finally, the capacitor is contacted by an arm as the vacuum head carrying it moves along the path, thereby disengaging it from the head and allowing it to drop into a receptacle. The capacitors may be subjected to a conventional firing at an elevated temperature to fully cure the coatings.

As a further aspect of the invention, it is contemplated that there may be cases in which it is desirable to provide conductive electrodes on a capacitor of a greater thickness than would normally be accomplished by a single dip and cure process. To achieve this, there are an odd number of vacuum mounting heads on the conveyor and the capacitors are loaded onto every other vacuum mounting head. Each capacitor makes two passes through the coating and drying equipment, and after the first loaded capacitor is double-coated, synchronized removal of every other capacitor beginning with the first is instituted. As in the case of a single dip, the coated capacitors are later fired at an elevated temperature to fully cure the coatings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a preferred form of apparatus for providing coated electrode terminals in accordance with the process of this invention.

FIG. 2 is a perspective view of a typical capacitor illustrated before coated terminals are applied.

FIG. 3 is a perspective view of the capacitor of FIG. 2 depicted with coated terminals.

FIG. 4 is a plan, partially sectional, view of a vacuum chuck for transferring uncoated capacitors from a supply receptacle to the coating conveyor taken along the line 4--4 of FIG. 1.

FIG. 5 is an enlarged, elevational view of capacitors mounted on the coating conveyor showing precision locating of the capacitors immediately prior to coating.

FIG. 6 is an elevational, partially sectional view of the coating apparatus taken along line 6--6 of FIG. 1.

FIG. 7 is an elevational view of means for changing the capacitor orientation after coating of one terminal and prior to coating another terminal, taken along the line 7--7 of FIG. 1.

FIG. 8 is a sectional view taken along the line 8--8 of FIG. 7.

FIG. 9 is a sectional view depicting a freshly coated capacitor within a curing lehr.

FIG. 10 is a sectional, elevational view of a coated capacitor immediately prior to removal from the coating apparatus.

FIG. 11 is an enlarged fragmentary view of a vacuum retention means.

DESCRIPTION OF A PREFERRED EMBODIMENT

With reference now particularly to FIGS. 2 and 3, a typical capacitor to which electrode terminals are to be applied is shown at 10 and includes a generally rectangular parallelepiped body form of an insulative material containing the capacitor electrodes within. As shown best in FIG. 3, in the practice of this invention coated terminals 11 and 12 are formed on the margins of two opposite sides. Each terminal consists of a continuous cap of conductive material enclosing the respective side and margin of the capacitor and in electrical contact with portions of the capacitor electrodes or plates (not shown) which extend outwardly of the insulative body. The coatings 11 and 12 are of uniform thickness and extend inwardly of the capacitor edge a precise predetermined amount.

As seen from above in FIG. 1, the apparatus of the invention, enumerated generally as 13, includes wheel shaped conveyor 14 powered to rotate about a central axis 15. A plurality of vacuum mounting heads 16 rotatably secured to the periphery of the conveyor individually carry the capacitors 10 successively through a first capacitor alignment station 17, first coating apparatus 18, capacitor edge orientation station 19, second capacitor alignment station 20, second coating apparatus 21, a pair of drying lehrs 22 and 22' and a discharge station 23.

In a way that will be more particularly described later herein, a plurality of uncoated capacitors 10 uniformly arranged in a line as at 24 by a conventional vibrator feeder are picked up one at a time and transferred to a vacuum mounting head 15 by a vacuum loading chuck 25 for processing as described above.

More particularly, the conveyor 14 includes a peripheral circular member 26 which includes a plurality of separate internal vacuum manifolds connected with a suitable air pump (not shown) by conduits 27.

For the following description of the vacuum loading chuck 25 construction, reference is made particularly to FIG. 4. An upper tray portion 28 of the vibratory feeder with the line of commonly oriented capacitors 24 is located below and outwardly of the vacuum mounting heads 16. As the capacitors are transferred to the conveyor, the vibratory feeder moves the capacitor line in the direction of the arrow to continuously maintain a capacitor in the leftmost or loading position.

The vacuum chuck 25 includes a cross-shaped body portion 29 affixed to an axially located shaft 30 for rotation therewith. At the outer end of each of the body portion arms, which arms are at 90-degree separation, there is provided an axially aligned hollow tube 31 onto which is removably received a sleevelike transfer head 32. The head 32 terminates in a hollow open-ended tube 33, the bore of which communicates through the bore of the head 32, tube 31 and passageway within the body portion 29 to a source of supply of low-pressure air (not shown). By means of a rotative power source 34 (FIG. 1) acting through the shaft 35, cam 36 and cam follower 37, the body portion 29 is successively indexed in 90 degree increments. The special cam and cam follower 36, 37 arrangement is what is conventionally referred to as a Geneva mechanism and details of operation are well known to those skilled in the art.

When a transfer head 32 is indexed into the lowermost position with the open end of tube 33 disposed opposite the first capacitor 10 in the line 24, a synchronized switch means (not shown) connects the bore of the tube 33 with a conventional vacuum pump (not shown). In this manner the capacitor is held to the end of the tube 33.

Next, the body portion 29 is indexed a further 90 degrees, bringing the uncoated capacitor just picked up from the line 24 to a position of engagement with the outermost end of a vacuum mounting head 16 as it moves therepast. Shortly after the capacitor engages a head 16, the synchronizing means disconnects the vacuum pump from the transfer head 32' holding the same capacitor, thereby transferring the capacitor to the conveyor mounting head 16, the specific retaining means being described below.

Turning now particularly to FIG. 8, each vacuum mounting head 15 includes a cylindrical shaft 38 with an inner flanged end 39 rotatably received in a suitably shaped opening of an outer wall 40 of the conveyor peripheral member 26. The outer surface of the shaft 38 within the wall 40 includes a pair of diametrically opposed recesses 41, which are so arranged as to receive a ball detent 42 carried within an opening in the wall 40. A coil spring 43 urges the detent against the shaft 38 and in that way two fixed rotational positions or stops exist at those points where the ball detent engages the recesses 41.

The outer end of the shaft 38 includes a reduced diameter portion 46 onto which is received a hollow, sleevelike capacitor retaining member 47. A spur gear 48 fits on the outer end of the larger diameter portion of the shaft 38 and includes a slotted hub 49 via which a pin 49' secures the gear, retaining member 47 and shaft 38 together as a unit. The retaining member 47 has a flattened tubular end 50 with a notch or recess 51. When a source of lowered air pressure is connected to the manifold associated with the respective mounting head, a capacitor is retained within the recess 51 by the air pressure force operating on both the facing surface and edge of the capacitor received in the recess. It is to be particularly noted that the relative dimensions of the capacitor and recess 51 are such that the bore opening within the recess is completely covered when the capacitor is retained therein.

As seen best by comparing FIGS. 7 and 8, the stop recesses 41 are so located as to orient the side of the capacitor retained within 51 in a vertical position. That is, when the ball detent 42 resides within one of the recesses 41, a first end of the capacitor is, say, pointed downwardly, whereas rotating the gear 48 and shaft 38 to engage the ball 42 within the other recess 41 brings that same capacitor end to an upwardly directed position.

The detailed construction of the coating apparatus 18 and 21 is seen best in FIG. 6. As open-ended tank 52 is fixedly mounted adjacent the conveyor 14 with its open end located under the capacitor path of movement. A mesh screen 53 for straining the liquid coating material 54 is anchored to the tank wall at a point substantially spaced from the open end. A fitting 55 in the bottom of the tank connects the coating material via a hose 56 to a circulating pump (not shown) for removing the coating material from the tank.

A coating wheel 57 with a peripheral groove 58 of uniform and predetermined depth is mounted on a horizontally disposed axle 59 for rotation therewith, which axle, in turn, is rotatably journaled in an elongated swivel plate 60. An L-shaped extension arm 61 integral with the plate 60 is pivotally affixed to the tank wall 52 as at 62, affording precise vertical positioning of the coating wheel upon vertical adjustment of other end of the plate 60. Rotative drive for the wheel 57 is provided from a power source (not shown) via a first sprocket chain 63, a first sprocket (not shown) affixed to a shaft 63 passing through plate 60, a second sprocket pinned to the shaft 63, a second sprocket chain 64, and a further sprocket (not shown) affixed to the axle 59 and located behind the coating wheel as depicted in FIG. 6.

A support 66 fixedly mounted with respect to the tank 52 includes an extension arm 67 having a threaded stop 68 for engaging the outer margin of the plate 60. A coil spring 69 interconnects the plate 60 and arm 67 urging them toward one another. Adjustment of the threaded stop 68 raises or lowers the end of plate 60, as the case may be, to position the coating wheel 57 accordingly. The upper end of the base 66 includes a table 70 for supporting a surface gage 71, the actuating or measuring arm 72 of which extends downwardly of the table to engage the upper surface of the plate 60 and measure the vertical position of the plate from a threshold plane in a conventional manner.

Means for applying coating material liquid or slurry to the wheel groove 58 and for removing the same is identified generally by the reference numeral 73. This means comprises a body member 74 having a curved concave portion 75 closely fitting about a corresponding part of the coating wheel circumferential periphery. A passageway 76 extending completely through the body 74 has its inner opening emptying into the wheel groove in the upper reaches of the wheel and its outer opening connected via a tubular fitting 77 and hose 78 to receive coating liquid or slurry from the pump. That is, coating slurry strained by the mesh 53 is removed from the tank 52 via fitting 55 and hose 56 and then pumped back through hose 78, fitting 77 and passageway 76 to fill the groove 58. The curved beveled wall surface 79 contacts the wheel periphery and serves to smooth the coating slurry upper surface in the groove and thereby insure continuous uniform depth during application to the capacitor, as will be described.

An elongated member 80 has its two ends pivotally secured to the body member 74 and tank wall 52 at 81 and 82, respectively, thereby affording the means 73 movement following corresponding movement of the wheel 57. A compression coil spring 83 engaging the outer end of body member 74 and the support base 66 resiliently urges the means 73 against the wheel 57.

On a lower surface of the member 74 is affixed a thin springlike metal blade 84 having an outer end of such dimensions and so located as to ride in the bottom of groove 58 at the lowermost wheel position. As the wheel rotates in the direction of the arrow, the blade strips out the coating material, preventing a buildup which could impair capacitor coating. The stripped off coating slurry falls into the tank and is strained and recirculated as already described.

In the event that relatively short capacitors are to be dipped by the described technique, it is important that the capacitor edge to be coated be specially aligned. The first alignment station 17 is located immediately adjacent and prior to the first coating apparatus 18. More particularly, as is shown in FIG. 5, the alignment apparatus includes an elongate, slightly downwardly curving plate 85, located above the centerline of the mounting heads 16 to engage the upper edges of the capacitors as they move therepast and urge them downwardly. That is, the plate 85 positions the short capacitors low enough so that the lower capacitor edges will all contact the bottom wall of the wheel groove 58 and in this manner insure that the lower edge of each capacitor is coated to an extent equal to the groove depth. If the capacitor is sufficiently long, alignment by the apparatus at 17 and 20 may be eliminated since the capacitor lower edge will automatically bottom in the groove 58.

After a capacitor has one margin coated as described, it is conveyed through the lehr 22 to the capacitor orientation station 19 and rotated to dispose another margin to be coated in the lowermost position. Turning to FIG. 7, the capacitor orientation station 19 is seen to include a horizontal rack 86 fixedly mounted adjacent the conveyor 14 and presenting a set of upwardly directed rack teeth 87 for engaging and rotating the gears 48 as they move therepast. The number of teeth 87 in the rack are such that an incoming gear 88, carrying a capacitor with its lower edge coated, will be rotated 180 degrees on passing through the station locating the coated edge in the uppermost position and aligning a capacitor edge in the lowermost position for subsequent coating. It will be recalled on reference to FIG. 8 that both coating positions are accurately defined by the detent ball 42 engaging the respective recesses 41.

After orienting the capacitor in 19, it is optionally aligned in the second alignment station 20, which is identical to the station already described and depicted in FIG. 5. The capacitor then has its newly positioned lower edge coated in the second coating apparatus 21, the latter being identical to the apparatus 18 previously described.

The capacitor with two opposite sides coated is next conveyed through a heating lehr 22 where the coating material sets up into hardened terminals. As seen on comparing FIGS. 1 and 9, the lehr comprises a hollow elongated cylindrical tube 89 which is curved to accommodate the curvature of the circular member 26. The tube 89, as shown best in FIG. 9, is fixedly mounted adjacent the path of travel of the capacitors carried by mounting head 16 and includes a slotted opening 90 in the inwardly directed wall extending throughout its length through which the vacuum mounting heads 16 extend. An electrical resistance heater 91 is integrally affixed to the lower wall of the tube 89 for heating the tube bore in a conventional manner. In practice, a coated capacitor 10 is conveyed along the central portion of the tube bore and is heated to such a temperature and for an extent of time sufficient to set up the coating material.

Reference is now made to FIGS. 1 and 10 and the details of the discharge station 23. Essentially, the station 23 includes a fixedly mounted arm 92, the end portion of which is slotted and located to engage a conveyed capacitor as it moves along the definite path. More particularly, the slotted end elements 93 and 94 are so spaced vertically that the head 16 passes through the slotted wall while the members 93 and 94 engage a capacitor carried thereby and remove it from retention by the head 16. A removed, fully coated capacitor is permitted to fall by gravity into a suitable receptacle.

Although the capacitors are now provided with hardened terminal coatings, they are not sufficiently formed to permit adhering an electrical lead by soldering or other means. Depending on the particular coating material used, the usual final step is to fire the capacitors at an elevated temperature for a prescribed period of time to fully cure the coatings. For example, in an actual construction using a coating slurry including powdered ceramic and metal, the capacitors are fired to a temperature of approximately 1,500 degrees F.

The total number of heads 16 on the conveyor has been purposely made odd in order to permit ready use of the aforedescribed apparatus for double-dipping a capacitor. To achieve this, the capacitors are loaded onto every other head 16 and make two complete passes through the equipment. As the first loaded capacitor finishes its second pass, and thus has both its terminals 11 and 12 double-dipped, the removal apparatus 23 is synchronized (by apparatus not shown) to remove every other capacitor beginning with the first one loaded. In this way, the same apparatus can be optionally utilized to provide single- or double-dipping runs.

Claims

What is claimed is:

1. Apparatus for coating the ends of elongated articles, comprising:

a conveyor turret including a plurality of vacuum chucks for indexing said articles through a loading station, at least one coating station, at least one heat treating station and an unloading station;

each of said chucks including a notched face conforming to the configuration of an elongate section of the article received thereat;

means feeding said articles to a transfer turret having a plurality of vacuum chucks;

said turrets being disposed and synchronized in movement whereby opposed chucks are paired in cooperative association to effect transfer of said articles from the transfer turret chuck to the notched face on the conveyor turret chuck;

means effecting said transfer of articles including valve means which at the time of common contact of an article with a pair of opposed chucks is adapted to connect the conveyor chuck to a vacuum source while simultaneously removing such vacuum from the transfer chuck;

a non-planar guide plate overlying the path of conveyor chuck travel and contacting an end face of the article conveyed whereby to slide said article along the notched portion of the conveyor chuck to effect a predetermined alignment of the other end of said article with respect to the coating means at said coating station; and

a coating means including a circumferentially grooved roller partially immersed in a pool of coating material and positioned to receive said other article end in said groove.

2. Apparatus as in claim 1 including means disposed subsequent to the heating station and adapted to rotate each conveyor chuck thereby inverting the article carried.

3. Apparatus as in claim 2 including additional coating and heating stations disposed subsequent to the means to rotate and operatively associated with the conveyor turret whereby each end of said article is coated.

4. Apparatus as in claim 1, in which said grooved roller is axially rotated during article coating in such direction that the portions of the roller immediately adjacent the article are moving in the same general direction as the article indexing movement.

5. Apparatus as in claim 1, in which the unloading station includes a fixedly mounted arm which engages a coated article as it is indexed through said unloading station and removes it from the associated conveyor turret vacuum chuck.