US1849885A - Condenser and process - Google Patents

Description

Mllch E5, R932. W; M PRESS dug coNDENsER AND vPROCESS Original Filed April 30. 1920 www@ mentioned.

atented Mar id; i932- @ne ci the rst steps in the process of inakingcondensers consists in assembling alter nate sheets of conducting and dieiectric niateriais to huiid up a condenser stack of the required height, these sheets oi materialA heing separated hy insulation having suitable properties tor this peculiar class of Work. Notwithstanding great cere in selecting these materials and in aernhiing them', it is a very common experience to have a condenser break down during test or whiie in use' and it has been deniteiy' determined that a very irnportant cause of such breakdowns is the pres,

ence or voids, gas, or an excessive amount o insulating material between the sheets of inaterial that maire up the condenser. i

it is an important object oi the present invention to devise a process of making condensers which will reduce to a minimum imperfections and faults of the character above in other Words, the invention aims to devise a process of huiiding condensers which will eiiininate an unnecessary thickness of insulating; material ToetWeen the layers of conducting and dielectric materials that maire up the condenser and which will also reduce to a minimum the presence of voids, hiisters or bubhies in the condenser. it is also an` object of the invention to devise a process oi making condensers Which rvili produce a condenser that is a firm mechanical mass, that will have a very low dielectric loss and in which the leakage between successive conducting; elements of the condenser Willbe reduced to a minimum. A further object of the invention is to improve condenser constructions hot-h from an eiectricai and also from a mechanical standpoint.

This appiication is a division of my copending appication lSerial No. 377,977, iiled April 30, i920, which has eventuated into Patent No. 1,721,503, dated July 23, 1929.

The invention also consists in certain new and original features of construction and CT EL'NTCLAIR,

CGE-@ELLE I GGBEQRATEGH NEW Biv'd and this application le rovember combinations of parts hereinafter set forth and claimed.

ilthough the nove/l ies-,tures which are he iieved to characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itseii, as to its objects and advantages, the mode ci its operation andthe manner of its organization may he better understood hy referring to the following. description with the accompanying part thereof, in which Fig. l is a front elevation showing in the process of manufacturing o a condenser constructed in accordance with the in vention and the apparatus used therefor;

Figs. 2 and 3 are side and vplan views Vo: the apparatus-shown in Figi; and

Figs. land 5 are pien and side views respectivey of the iinished condenser.

Like reference characters denote like parts in the several figures of the drawings. i

in the oiiovving description and in the ciaims parte will he identified by speciic names for convenience5 Tout they are intended to he as generic in their application to similar parts as the art vviil, permit.

ssuining that fthe mica or other dielectric elements to he used in the condenser have been made hy splitting the mica sheets to the desired thickness and cutting them out to the required shape and dimensions, and also that the tin foil or other conducting elements of suitable shape and size have been provided the next step is to coat'the mica elements Withvarnish or other adhesive insulating material. is desirable that this coating shall be very thin and that it shall completely cover both surfaces of each mica sheet. This coating' operation may he performed in any suitahie manner and with any suitahle insulating material, such for exarnpie as varnish.

After the dielectric elements have been coa-ted and partially dried, they are next rauen lin connection drawlngs 'forming a assembled with sheets of tin foil, or other conducting material of the proper size and shape, to form a condenser stack. The condenser stack may either be built up in the form of a tall stack that later is split up into units of the required height, or the stack may be built up in the form of individual units, each unit stack being kept separate from the others.

After the assembly of the stack has been completed, the stack is next heated or baked for the purpose of driving out the solvent in the varnish, eliminating any excess of var-l nish between the elements, and-driving out any gas'or vapor that may be pocketed between the elements of the stack. A further result accomplished in the baking operation when certain varnishes are used is the oxidizing or chemical changing of the solid opnstituents of the varnish.

For this purpose the condenser stack preferably is transferred to a baking stand of the general character illustrated in Figs. 12 and 3.

Assuming that the condenser stack has been assembled in units, as above described, these units are placed one above the other in a stand which comprises a base 16 and two posts 17 and 18 rising from the opposite sides oit the base and threaded near their upper ends. The individual units are separated from each other by separator strips 19 of brassl or other suitable material having holes drilled in them so that they slide freely on the posts 17 and 18.

Each unit is located between two metallic spring plates normally convenly curved or bowed with reference to the condenser, as

' clearly' shown in Fig. 2, one of these plates being designated at 50 andthe other at 51. lt will be seen that the plates are alike in construction and that each plate is provided at opposite ends with projections extending at substantially right angles to the plate and designed to lit over the opposite sides or edges of 'the condenser unit. Ears 52 and 53 also project on these plates and have holes punched in them. The parts 50 and 51 consist preferably of a metal which can be easily bent or shaped to form the intermediate spring portions and the rigid angular projections. Any suitable sheet metal is adapted for this purpose, such as steel or phosphor bronze. ln assembling the parts 50 and 51, the spring portions are arranged I on opposite sides of the stack with their convex surfaces facing the same and in, parallelism with the sheets composing the stack.' rlhe are then compressed flat against the stack and rigidly secured at opposite sides as hereinafter. described to maintain lthe sheets together under spring compression.

The clamp comprises two parts which lcan be cheaply' made and easily assembled to maintain the stack under good compression Lacasse and at the same time allow the leads to be brought out at opposite ends of the stack,-` the stack projecting at opposite ends beyond sure plate 22 at its lower end and threaded through a yoke or plate 55 which is removably secured to the upper ends ot' the rods 17 and 18,. The handle 56 is secured to this screw and allords a convenient means for `turning it. It will be seen that with this arrangement the entire stack can be compressed until the springs 50 and 51 are straightened out, thus compressing the units with a spring pressure. The baking stand with the stack lof condenser units clamped therein is then placed in an oven and baked for several hnurs at a temperature oiapproximately 110 to 115o C.

While tbe greater part of the solvent in the varnish coating of the dielectric elements is eliminated before these elementsV are assembled to form acondenser stack, a certain amount of solvent still remains in the lower layers of the varnish coating Furthermore, the coating is thicker than is necessary. The baking of the stack while it is maintained. under a heavy spring pressure squeezes out the surplus varnish which softens under the relatively high degree of heat to which it is subjected. At the same time this comparatively high heat vaporizes the solvent together with any other vaporizable elements, such for" instance as traces of water5 which may be pocketed between the Sheets, and the heat, together with the pressure, c'o-operate to reduce to a minimum gas, vapor, and the thickness of the adhesive remaining between the sheets. ln other words, theheat tends to diluse any gases or vaporizable materials present between the sheets while the pressure tends `to squeeze out these materials from between the sheets of the stack. When separator plates 19 made of brass or similar material are used,as distinguished from insulating material, they serve not only to separate the units and give the stack additional mechanical ri idity, but alsoto conduct yheat into the interior of the stack and thus to facilitate the baking operation.A The oven is lUU lla)

ventilated during the baking operation for the purpose of carrying oil' the solvent vapors and also, when an oxidizable varnish such i as copal varnish 1s used, to provide an ample supply of oxygen to eect this oxidation.

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described elimination of the greater part o:A

tbe solvent from the varnislicoeting on the dielectric elements before these elements are assembled to forni e condenser stack. This leaves only enough solvent in the coating to cause the coating to soften becorne sticky during tbe baking operntion, which result is desirable et this tirnelor the purpose of adbesively securingv eil 'the sheets of materiel firmly together, and since only e relatively small quantity of solvent still remsins in the costing, the eliniinstion or thesolvent can be made rnucli more. complete by the bulging;

step would otherwise be practicable. further udvun'tageous result produced by this process is tbe sealing; of lthe marginal spaces between adjacent dielectric elements of the stack. Esch conducting element lying on e mica sheet is surrounded on three sides by en inactive` or@ rnics; that is, nn ares. of mice that is not subjected to tile dielectric strain. This margin covered with varnislil during the costing operation, es above described7 end the compression to which tlie condenser steclris not subjected to tbe dielectric strain. liis margin is covered 'with varnish during the costing operetion, es -ebove described, end the compression to which the condenser stack is subgected during the bal-- ing operation results in squeezing additional varnish out from between the overlapping sheet and into these rnnrginal spaces.

rl'his varnisl'i completely se'sls tbe space between the inactive margins of adjacent dielectric elements. lt vvill be understood that when a condenser is in -use there is n ndency for the current to. discharge. from the edge of one of the conducting elements ecross the inactive margin to the edge of the next adja- .cent conducting element. rdinarily, e comparatively free patin is left ortbis dis charge over the surface of the mica. The sealing ol these marginal spaces, however, by varnish introduces s solid wall of insulating material in the path of this discharge and thus reduces very substantially tbe surface leakage that otliervvise would be present in the condenser. In other Words, this construe tion reduces the electrical loss in the condenser.

After the locking operation has been cornm pleted, tlie condenser will be found to be ek firm, mechanical mass capable ol withstanding 'very rough usage. The sealing of tlie edges, as above described, contributes to this result and also is of advantage when the condenser is to be used in a deinp location.

After the condenser has been baked its manufacture muy be completed in any desired manner. According to the process which l prefer et present, the condenser units are next tested end any units which fail to withstand tlie tests are discarded. lln order to reduce still :further the electrical losses in the condenser and else vfor the purpose of improving its mechanical structure, it is preierable under sonne conditions to repeat the bebng operation.

rEllis second bulging need not be continued sslono es the first but usually is from sinl to eight nours et s temperature from il() degrees to 115 degrees C. The exact nature of the change produced in the condenser by this second baiting is dicult to determine but probably is due to scene change produce-d in the exceedingly thin lilm of vsrnisli that still remains between the sdjecent elements of the condenser. lieve. detrrnined, however, by actual test tiiat the electrical characteristics o? tbe condenser are improved by tliis second l baking and that they can be still further lmproved by e tliird or ourtli 'lClie degree of improvement, liovvever, decreases with successive belrings usually it is not advisable from u manufacturing standpoint 'curry die condenser through more tiren two or these lient cycles.

.The or beting, end il desiredelso, tile relieating or subsequent baking operations ere performed in tbe-manner ebove described, but after tbe locking operation tias been coinpleted the projecting ends oit tbe spring plates which lis-ve ncrv been brought' into overlapping relationship et opposite sides of each unit, are permanently secured together by soldering or Welding. Preferably this securing operntion is perfor ed by spot vvelding, as indicated at 5'?, lig. 5. Tae condenser terminals 58, 59 are sliovvn in, l und 5 connected to tile `foil sheets projecting 'lroni the stack. As shown in Fig. fl the integral parte 52, 53 ere formed with holes fior securing the finished condenser in piece.

This process results in enclosing tbe condenser staclr in e casing which because of its resilient nature and tbe manner in which it is secured on the steclr, exerts a permanent spring pressure on the stack over substantially its entire active areas. After the securing operation the units may be removed from the baking stand.

rlbe connections tothe op 'te sets of conducting elenients can be madigsiln any convenient'inanner es, for instance, by soldering leeds l58 und 59 to these conducting elements respectively, with a suitable soft solder. The punched ears 52 and 53 are provided to facilitete the securing of the cornpletedcondenser lll@ to its support. rlhis construction provides a very compact and ecient condenser especially adapted for locations where the condenser is subjected to rough usage.

While certain novel features of the invention have been shown and described andare pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes in the' forms and details of the device illustratedand in its operation may be made by those skilled in the art without departing from the spirit of the inven tion.

What is claimed is:

1. A sheet condenser which consists of a stack of interleaved liat sheets of mica and metal foils, the foils of opposite potential eX- tending out from spaced-apart portions of the side of the stack; and a two-part metal clamp, the two parts of which extend. tlat over substantially the entire surfaces of the two faces of the stack; one of said clamp-parts tending to assume a convexly curved shape With reference to the stack-face which it engages and said part-s having portions extending over portions of the side of the stack other than those from which the foils extend, to overlap one another; and said overlapped portions being permanently secured together While said convex part lies substantially flat against thestack, whereby the stack is held under permanent spring compression.

2. The combination with an electrical condenser stack of Amica and foil sheets, of two metal plates holding the stack between them in the direction of its height, and means for holding the stack under pressure between said plates; at least one of said plates being con- 'structed to tend to assume a convexly curved shape and having its bowed portion arranged to bear against an end of the stack, said plate being substantially straightened under said pressure.

ln an electrical condenser, a stack of condenser elements and a clamp for said stack comprising members engaging opposite sides of the stack, at least one of said members having integral lateral portions connected to the other member, at least one of said members Ahaving a springy portion parallel with said elements whereby the elements are held together under spring compression.

4. ln an electrical condenser, a stackof condenser elements and U-shaped spring clamping members having intermediate portions engaging opposite sides of the stack and connected together, holding the members against the stack to compress the elements together under spring pressure.

5. In an electrical condenser, a stack comprising alternate sheets of conductor 4wand dielectric and a multi-part open ended sheet metal clamp for the vstack and comprising metal plates upon opposite .sides of the stack and integral lateral overlapping portions se curing the parts together in clamping relation against -the stack.

6. In an electrical condenser, a iiat faced stack comprising alternate lat sheets of conductor and dielectric and a multi-part metal clamp for the stack and comprising plates lying flat upon and extending over substantially the entire surface of nthe opposite dat faces of the stack and having integral portions extending at angle with the plates and along the sides of the stack and connecting the parts together in permanent clamping relation against the stack.

7. in an electrical condenser, a stack comprising alternate sheets'of conductor and dielectric and a multi-part metal clampv for the stack and comprising spring plates engaging opposite sides of the stack and having integral rigid lateral portions overlapping each other and securing the parts together in clamping relation against the stack under spring pressure.

8. ln an electrical condenser, a stack comprising alternate sheets of conductor and dielectric and a sheet metal clamp for the stack and comprising plates engaging oppositel faces of the stack and angularly arranged integral lateral portions bent to connect the plates together in clamping relation against the stack, at least one of said plates being a. spring and adapted to assume a concave-con'- vex shape when/released.

9. ln an electrical condenser, a stack comprising sheets .of lconductor and dielectric and metal spring plates upon opposite Asides of the stack and connected together along opposite edges of the stack transversely of the sheets to hold the sheets in contact under spring pressure.`

10. ln an electrical condenser, a. stack comprising sheets of conductor and dielectric and a clamp for said stack comprising spring members upon opposite sides of the stack and means connecting them and extending along opposite edges of the 'stack and trans- M0 versely of the edges of the sheetsfor maintaining said Vmembers in clampingrelation against the stack holding the sheets togethen underuspring pressure.

11. In an electrical condenser, a stack comprising alternate sheets of conductor and dielectric and a sheet metal clamp for the stack comprising parts at opposite faces of the stack, at least one of which is springy, and integral rigid lateral portions bent to extend along opposite edges of the stack and connecting the parts together in clamping relation against the. stack, holding the latter under spring pressure.

l2. ln an electrical condenser, a stack comprising alterna-te sheets of conductor and dielectric and sheet metal spring plates engaging opposite sides o-said stack, at least one of said plates having integral lateral portions bent to extend along opposite edges of the Leccese stack to connecty the plates together, clamping the stack under spring pressure, said plates being formed` to assume a concavo-convex shape when released with the convex sides facing the stack.

13. An electrical condenser comprising a stack of dielectric and armature material, a. metal end member for said stack having portions adapted to extend along opposite sides of said stack, saidiencl member having its side port-ions diverging from the stack and being pre-shaped to move said side portions inwardly toward the stack on the application of pressure to said end member.

In testimony whereof hereunto aiiix my signature.

WILLIAM EL PRIESS.

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