US2574686A - Method of impregnating electrical coils - Google Patents

Description

Nov. 13, 1951 R. 1.. BROWN METHOD OF IMPREGN ATING ELECTRICAL COILS IN VEN TOR. RAYMOND L. BR OWN ATTORNEY 2 SHEETS-SHEET 1 Filed Aug. 26, 1948 Nov. 13, 1951 R. L. BROWN 2,574,686

METHOD OF IMPREGNATING ELECTRICAL COILS Filed Aug. 26. 1948 2 SHEETS-SHEET 2 INVENTR. RAYMOND L. BROWN Wj JUYORNE.

Patented Nov. 13, 1951 METHOD OF IMPREGNATING ELECTRICAL COILS Raymond L. Brown. Darien, Conn assignor to Electrolux Corporation, Old Greenwich, .Conn" a corporation of Delaware Application August 26, 1948, 'Serial No. 46,262

1 Claim.

This invention relates to a new and improved method of making electrical windings and the new and improved coil unit fabricated therefrom.

In a particular embodiment of this invention, it is especially described herein as incorporated in an apparatus adapted to make armature windings imbedded in a resin matrix. This disclosure embraces an apparatus as well as a method for bonding electrical windings into a relatively solid matrix type of structure, and in addition relates to the matrix structure obtained by resorting to such a process of manufacture.

Heretofore, a number of different processes have been devised such as brushing, dipping and the like, in order to eifect the coating, impregnation or similar processing of wound coils with insulating varnishes of one kind or another. Invariably, such processes necessitated the lapse of :a considerable time interval between the impregnating step and the production of the final, completed unit. Frequently, 6 to 10 and even 12 or more hours were required when a long baking iperiod was'involved. In some cases a long drain age interval, in addition, was necessary to allow for removal of excess coating material from the outer surfaces of the windings.

In the past, although a number of labor-saving devices have been introduced in methods of electrical coil processing in order to effect certain economies of time, eifort and materials, no

completely satisfactory solution has as yet been reached. The former processes were critical and the degree of success attained depended, usually upon the ability and skill of the operators. In many instances the results attained prior to the present invention were limited by the variations occurring from batch to batch of the resin and solvent compositions used. Invariably, a considerable personal equation was always heretofore present. Such former procedures therefor gave results which were obviously unreliable and yielded products which varied over too wide .a range for their satisfactory embodiment in "industrial or large scale assembly-line methods of manufacture.

.It is an object of this invention to provide a continuous method of operation for the large scale manufacture of impregnated electrical windings.

Another object hereof is to provide a process wherein no solvent materials are used to effect the impregnating step.

Still another object is to avoid the dipping and drainage steps heretofore almost invariably practiced.

It is another object to coat and impregnate only those parts requiring such treatment and to avoid the coating of such extraneous parts :as

the shaft, commutator, armature core and the like.

A further object is to eliminate :any subsequent cleaning operations such as those necessitated by the removal of resin from the inexpediently coated portions resulting from the processes as heretofore practiced.

Still another object is to insulate, seal and. bond the individual turns of wire forming the coils of an armature, electromagnet, or similar structure to form a composite unitary or matrixlike structure.

Still other and further objects will become apparent upon reading the following description incorporating various illustrative embodiments of the invention.

In general, this invention attains the above and other objects and advantages by providing an assembly-line technique whereby a number of woundelectrical coil units on a conveyor chain are passed through a series .of steps to obtain an improved composite product.

.In order to facilitate a more complete understanding of the principles of this invention, a number of drawings forming a part of this disclosure are included herein and illustrate clearily a preferred embodiment of the invention.

In the drawings:

Figure 1 is a fragmentary perspective view of an assembly-line type of apparatus for carrying out the method of the present invention;

Figure S2 is a perspective view of an armature impregnated in accordance with the methods herein described, and sectioned so as to show the extent of impregnation and internal bonding effected by following the methods disclosed herein.

Broadly, this invention is predicated upon the discovery that certain heat hardenable resins in liquid form and without the aid of a thinner or solvent can be flowed upon predetermined portions of a wound coil element, such as an armature which has been previously heated, and by rotating the element, the resin at first becomes more highly fluid by contact heating, then'pene'tra'tes thoroughly throughout the windings and by subsequent continued heating the penetrated and surface resin gels or sets up in s'itu whereupon a further baking at a higher temperature polymerizes the gelled resins to form a solid matrix-like unit.

Referring now in more detail to the drawings the elements H to be impregnated with a resin are supported on :a conveyor chain I3 by which each individual element is conducted past certainprocessing stations such as the pre-heating 'unit 15 consisting of a bank of infrared lamps or a steam heated radiator or the like.

Each element is inserted and supported free for-rotation in a carrying frame It fulcrumed at ilfor outward rotation by passing the shaft [9 (see Fig. 2) through the opening in the inner race of ball bearing member 23 and holding shaft I9 in place by a key '21 inserted and spring tensionedin a groove cut in the shaft l9. v

"Since the'resin'isto be applied to the exposed coil ends only, a guide-rail 23 is provided-for lifting the 'armatures I I from their "vertically susresin being supplied through tubes 29 which convey the resin from tank 3| through metering means of pinchcocks 34 in each line.

' processing, for insertion into a completely'assem- Cooling to proper impregnation temperature (on guide-rail 23) 3 pended position until they assumea horizontal alignmentas at position 24 whereupon they are Impregnating and penetrating (at lowered into frictional contact with a faster movor portions upon passage of the armature windings beneath the spouts 21 at station 31, the

pump 33. The correct amount of resin is applied at each station by controlling the flow by The resin becomes warmed upon contacting the heated windings and is thereby rendered more highly fluid thereby further facilitating coil penetration.

Simultaneously, the rotation of the armature distributes the liquid resin over the windings in such a way as to insure its being evenly spread thereover and thus effects a uniform resin penetration through and between the individual wires of the coils, i. e. 35, Fig. 2, as well as between the windings and the walls of the coil slots cut in the armature, i. e. 33, Fig. 2. If additional portions'of resin are necessary, one or more additional liquid resin depositing stations, asindicated at 38 and 39, are provided in sequential locations to apply successive doses of resin. The result is a wound armature unit the coils of which are impregnated with a resin which insulates, seals and bonds the coils in fixed position in a matrix-like structure which is simultaneously bound to the walls 40 of the core slots. I

Only the windings and the portions interior to the core slots are coated and impregnated. The subsequent heat treatment in unit 4| (one lamp only of which is shown) results in an accelerated gelation or set-up of the applied resin while the higher baking temperature of unit 42 results in i the heat hardening or polymerization of the resin in and around the impregnated coil units. Since no part of the resin covers the armature laminations, or the commutator or even the outer surfaces of the slots themselves, no further processing, cleaning, scraping or similar resin removal step is necessary. 7

Furthermore, the rotation of the resin coated armatures results in an even distribution of the impregnating resin throughout the windings. The entire operation is a continuous process necessitating a minimum of handling and a minimum supply of impregnating resin.

The product obtained is a dynamically balanced unit ready, without too much further detailed bled motor frame.

In order to facilitate the complete comprehension of the principles and practice of the present invention the full details of one complete cycle of operations is given below:

Cycle timing Preheating (in unit l5) llminutes 9 mi e The temperatures attained by each armature in its passage through the various steps during the cycle are as follows:

C. F. At the end of the preheating (exit from '44 unit I5) 118 At first jet (at position 31) 81 1'78 At start of resin set-up (gelation at position 43) 68 At end of set-up (after passage through heating unit 4|) 123 253 At end of bake (after passage through baking unit 42) 134 273 After the armatures are inserted in their individual carriers l6 at station 50, they enter the preheat chamber l5, where their temperatures are raised to about 240 F. in order to dry the insulating paper and cotton insulation. Then while being lifted on rail 23 they are allowed to cool down to approximately 180 F. at which point the first dosage of resin is applied. Such a temperature as causes the resinapplied'to thin out and run readily into the slots and between the wire windings, but not high enough to effect gelation, is used. Too cold an armature retards penetration of the resin, while too high a temperature effects gelation and even incipient polymerization and hence is undesirable at this point.

In the embodiment shown in Fig. 1, three sets of jets are used, spaced to apply the resin to three armatures simultaneously. This is necessary only when the required amount of resin cannot be applied in one shot or dose during the short time interval (approximately 1 minute) that the armature is under one set of jets. In

practice approximately 60% (i. e. 8 to 10, cc.) of the total quantity of resin is applied during the first shot at station 31 and is directed on the end turns of the winding close to the iron laminations at both ends thereof. The second shot of resin at station 38 is delivered after thelapse of somewhat more than one minute during which the first shot has been spread over and has been soaked into the coil windings. It is applied at station 38 and also on the end turns but this time near the shaft and on the paper washer 5| and tie band 52 near the commutator. If necessary a brush 53, Fig. 1, may be lowered into position to spread the resin over the tie band. The third shot of resin is applied to the windings after another lapse of somewhat more than a minute at station 33 and is again applied near the iron laminations in order to fill the voids left by the imbibition or soaking in the first and second doses of resin. Each of the latter two doses applied are equal to approximately 20% (i. e. 3 cc.) of the total amount of resin required.

During the resin application steps and throughout the heating step eifected in unit M, the gelation or set-up stage, the armatures are rotated at about 40 R. P. M. in order to prevent any running ofi" of excess resin and in order to distribute the resin evenly and eifect uniform impregnation of the windings. The rotation is continued until the resin has had time enough to set-up or gel in situ.

From the set-up or resin gelation chamber ll, the armatures are carried into the baking chamber 42 where due to previous fixing or gelation of the resin the armatures may be again allowed to resume their vertical positions. The temperature in the baking chamber 42 is held at about 260 F. to 270 F. (approximately 134 C.) in order to eifect complete polymerization of the resin matrix.

Timing switch 54, Fig. 1, closes a circuit for the controlled operation of metering device 33 and the delivery of the predetermined supplies of resin to the jet feeding stations 31, 38, and 39.

In the practice of this invention, a monomeric or similarly constituted resin, i. e. dimeric type of liquid resin, is used and since the entire substance of the precisely measured resin portion or portions applied by metering pump 33 sets up or heat-hardens, there is no problem of drainage of excess or removal of contained solvent. Thus the prolonged drainage step heretofore necessitated is herein entirely eliminated.

The present process utilizes all of the impregnating compound applied to a coil by taking advantage of carefully and preferably volumetrically metered portions of resin intermittently applied after the passage of timed intervals, during which intervals the previously applied dosage has ample time to permeate the windings by capillary action. This impregnation step is further accelerated by increased fluidity of the resin resulting from temperature increase of the applied resin upon contact with the previously heated armature and winding as a step preliminary to resin application. The impregnated winding is subsequently subjected to an additional higher and further heat treatment sufiicient to effect gelation in situ after which polymerization and internal bonding, sealing and matrix formation by a final high temperature baking step is efiected in the final stages of the process.

Thus the prior processes necessitating dipping and drainage steps requiring 6 to 12 hours, or more, for completion are herein entirely superseded. Since the shaft, commutator, armature core, etc., are not coated or impregnated, no cleaning of these parts is subsequently necessitated. Instead, the final matrix-like unit emerges from the impregnating step as clean as when it entered this particular processing step. Moreover, the absence of a solvent obviates the taking of any of the precautions accompanying bubble or vapor-lock formation internally of the windings, such as accompanies the former vacuum, pressure, etc., impregnation processes. In addition, any fire-hazard due to explosive vapors, any shrinkage accompanying solvent evaporation, and the like are eliminated. No portion of the coating and impregnating compound of the present invention is lost by evaporation, dripping or otherwise.

Although as a preferred resin, 9. monomeric or liquid dimeric type of resin has been suggested,

and especially one which becomes less viscous upon slight temperature rise preliminary to polymerization has been mentioned above, it is to be understood that various other resins of the unsaturated polyester type either individually or in admixture with various other heat hardenable resins of a heat polymerizable type may likewise be used. Thus substituted unsaturated polyesters, alkyd unsaturated polyesters, or copolymers with styrene and similar heat hardenable resins containing from 2 to 5 percent of a polymerization catalyst such as benzoyl peroxide and tri-cresyl phosphate are readily adapted for use in this process.

It is to be understood that the examples given are merely illustrative and not limitative embodiments of this invention and that the scope thereof is to be determined solely by the appended claim.

I claim:

The method of coating and impregnating an electrical motor armature having wound coils portions of which are disposed in slots while the end portions are exposed comprising the steps of preheating the armature, positioning the axis of the armature in a substantially horizontal plane, rotating the heated armature about its axis, transversely moving the rotating heated armature across the path of a first pair of spaced streams of solventless impregnating and coating agent consisting of a, mixture of a copolymer of an unsaturated polyester and styrene, directing said first pair of spaced streams of said solventless impregnating agent onto the exposed end portions of the coils of said armature to apply approximately 60% of the total coating, transversely moving the rotating heated armature across the path of a second pair of spaced streams of said solventless impregnating agent, directing said second spaced streams of said solventless impregnating agent onto said exposed end portions of said coils of said armature to apply approximately 20% of the total coating, transversely moving the rotating heated armature across the path of a third pair of spaced streams of said solventless impregnating agent, directing said third spaced streams of said solventless impregnating agent onto said exposed end portions of the coils to said armature to apply approximately 20% of the total coating, whereby the coating spreads in opposite directions to impregnate and coat the coils, and further heating the armature while rotating the same to set the coating on the windings.

RAYMOND L. BROWN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,455,199 Groten May 15, 1923 1,675,419 Meyers July 3, 1928 1,848,344 Gofi Mar. 8, 1932 1,858,870 Apple May 17, 1932 1,875,205 Apple Aug. 30, 1932 2,116,318 Miles May 3, 1938 2,274,610 Goodwin et a1. Feb. 24, 1942 2,411,180 Alexander Nov. 19, 1946 2,414,525 Hill et a1. Jan. 21, 1947 2,464,568 Flynn et al Mar. 15, 1949 2,484,215 Foster Oct. 1 1949

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