US3904724A - Method of compacting powdered resin into slots of magnetic cores - Google Patents

Abstract

Apparatus for shaking and compacting heat-hardenable powdered resin into interstices between coil windings in a slot of a core of magnetic material, including a vibrating perforated table, clamps adjustably mounted on the table for holding a core in place with the slot in vertical position, a vibrator mounted under the table for shaking the core vertically, and a hopper under the table for collecting excess resin when powdered resin is spread over the upper open ends of the slot.

Description

States Patent lfiipple et al.

[4 1 Sept, 9, r975 METHOD OF COMPACTING POWDERED RIESlN llNTO SLOTS OF MAGNETlC CURlES Inventors: llarry l. lfiipple, Pittsburgh, Pa.;

Virgil ,l. Cozzarin, Clarence, N.Y.; Francis C. Kapperman, deceased, late of Eggertsville, N.Y., by Dorothy M. Kapperman,

administrator Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

Filed: Mar. 30, 1973 Appl. No.: 346,533

Related US. Application Data Division of Ser. No. 71,933, Sept. 14, 1970, Pat. No. 3,752,1 16,

llnt. Cl B2811) 1/08 Field 011 Search 117/18, 20, 21, 161 R, 117/161 ZB, 62; 118/57, 308, 406, 425, 408; 425/456; 264/71, 272

and 1 '1 1 1 11 1 m a a [56] References Cited UNITED STATES PATENTS 754,581 3/1904 Magnus 117/20 3,030,597 4/1962 Piaia, Jr. et a1... 264/272 3,261,707 7/1966 Korski et al. 1 18/406 3,549,582 12/1970 Payne et a1. 117/161 ZB Primary Examiner-Charles E. Van Horn Assistant Examiner-Jerome W. Massie Attorney, Agent, or FirmR. D. Fuerle [5 7 ABSTRACT Apparatus for shaking and compacting heathardenable powdered resin into interstices between coil windings in a slot of a core of magnetic material, including a vibrating perforated table, clamps adjust ably mounted on the table for holding a core in place with the slot in vertical position, a vibrator mounted under the table for shaking the core vertically, and a hopper under the table for collecting excess resin when powdered resin is spread over the upper open ends of the slot.

2 Claims, 2 Drawing Figures PATENTEDSEP' 1 1 3, 904-, 724

'HHH (mu FIG I 78 if MUFFLER 80 MUFFLER 9 90-"lOOp sI SUPPLY wyw FIG. 2

METHOD OF COMPACTING POWDEREI) RESIN INTO SLOTS OF MAGNETIC CORES CROSS REFERENCE TO RELATED APPLICATION This application is a division of S.N. 71,933, filed Sept. 14, 1970, now U.S. Pat. No. 3,752,116. Thisinvention is related to application Serial No. 61.106, filed Aug. 5, 1970 now U.S. Patent 3,710,437.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to apparatus for shaking powdered resinous material into interstices located between coil wires and between coil wires and side walls forming slots of a core of magnetic material, whereupon subsequent heating the powdered resin is fluidized and cured in place in order to avoid the existence of cavities within the core slot.

2. Description of the Prior Art Rotating electrical apparatus such as motors and generators, employ insulated coils comprising central core portions and end turn portions. The preparation of coils, windings, or conductors for insertion into slots of magnetizable cores by prior methods has involved the time-consuming and costly process of applying insulation tape, wrappers, and slot cell liners to the coil portions, such as disclosed in U.S. Pat. No. 3,054,880. The process was particularly involved where it was employed in the repair of coils for motors and generators.

A method that would eliminate or reduce the amount of taping and wrapping required on all types of rewound rotating apparatus would be desirable. In addition to reducing the labor required in the rewinding of the coil windings, a reduction of subsequent treatment cycles has been sought. More particularly, in the area of form-wound coils for stators, rotors, and armatures, with, for example, direct current fields and rotating fields, the methods remain the same; i.e., mostly handtaping of the assembled conductors, varnish treatment, and approximately 12 hour baking cycles.

The foregoing problems are of greater moment where repair shops for such apparatus are involved. Repair shops handle apparatus of various sizes and are therefore necessarily faced with a wide variety of nonstandardized coil shapes and sizes and different varnishes requiring different applying and curing procedures. For example, repair shops must be prepared to handle components of rotating apparatus varying in diameter from about 6 inches up to 6 feet or more. In such circumstances, the methods employed must be adapted to a maximum output at a minimum cost.

SUMMARY OF THE INVENTION It has been found in accordance with this invention that the foregoing problems may be overcome by winding coils into the slot of a core of, for instance, a stator, packing the interstices between the coils and core walls with powdered fusible resin material of fine mesh by vibrating or shaking the stator while pouring the powdered resinous material onto the open top ends of the slots so that the material descends into the slot and fills the interstices between the conductors and the core walls where the powder particles lodge and become compacted in place and accumulate until all voids and cavities are filled, whereupon the assembly of the stator and the resin filled slot is ready for a subsequent heating operation in order to fuse and cure the resinous material in place.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view showing the shaker device with a stator of an electric motor mounted in place; and

FIG. 2 is a schematic view of the air system used for operating the shaker device.

DESCRIPTION OF THE PREFERRED EMBODIMENT The device of the present invention is generally indicated at 10 in FIG. 1. It includes a base 12, a hopper 14, a vibrating table 16, clamp means 18 for holding a workpiece, such as a stator 20 fixedly in place, and a vibrator 22. The device 10 may have any peripheral shape such as circular or rectangular, so long as it is suitable for accommodating stators 20 of any size ranging from as low as, say, about 6 inches up to 40 inches or greater in diameter. The preferred general configuration of the device 10 is a square in the plan view which is the configuration shown in FIG. I which is a vertical sectional view, taken diagonally of the square.

The base 12 is preferably composed of metal channel members 24 of which there are four disposed in two parallel pairs on opposite sides of the device 10. Adjacent pairs of members 24 are secured together at their corners, such as by welding, to form a rigid square base. At each corner a leg 26 is disposed below the channel members 24 and a grooved wheel or castor 28 is provided under each leg. Thus, the device 10 may be mounted on a pair of tracks for movement between two or more work positions, such as placement of the base under a crane or hoist for lifting a workpiece of stator 20 in place and subsequently moving the device 10 away from the area under the crane.

The hopper 14 includes inclined plates 30, the upper peripheral portions of which are attached to the upper side of the base 12. The lower ends of the inclined plates 30 are provided with a discharge spout 32 having suitable valve or gate 34 for emptying the hopper of excess powdered resin 36 when a sufficient amount of the resin accumulates in the hopper 14.

The vibrator table 16 includes a perforated plate 38 having a plurality of openings 40 through which the excess powdered resin 36 passes from the stator 20 to the hopper 14. A peripheral flange 42 extends around the outer edges of the plate 38. The plate 38 is mounted on suitable support members which may be a pair of crossed I-beams 44 each of which extends diagonally from opposite corners of the device 10. The outer extremities of each support member or beam 44 is supported by a leg 46 such as a metal angle member the upper ends of which legs are secured to the beams 44 in a suitable manner such as by welding (not shown).

As shown in FIG. I, the upper portion of the device 10 including the vibrator table 16 is separated from the lower portion of the device including the frame 12 by elastic or resilient mounting means at each corner including elastic connectors 50 composed of rubber or similar material in order to facilitate the vibration of the table 16 and to prevent the base 12 from having a dampening effect upon the vibration. Particularly good results have been obtained when the conductors 50 are inflatable cushions having internal air pockets 52 which are filled with compressed air at a pressure of such as 150 pounds per square inch by similar air conduits 54 leading from a source of supply of compressed air. The upper side 56 as well as the lower side 58 of the air connectors 50 are secured to the adjacent metal plates 48 on the top side and 60 on the lower side by vulcanizing in a manner well known in the art.

When the device is not in use, the air connectors or cushions 50 are deflated so that the lower ends of the legs 46 rest upon support blocks 62 which are mounted on the channel members 24. As a safety member, each block 62 has a flange 64 which extends upwardly and adjacent to the corresponding leg 46 for maintaining the table 16 in alignment with the base 12, as shown in the drawing.

The clamp means 18 includes a plurality, and preferably four, chuck-like clamps that are adjustably mounted on separate guide ways 66. Each guide way 66 extends from one corner of the table toward the center of the device 10. The guide ways 66 are mounted on and supported by the support members 44. Each clamp is movable along its corresponding guide way 66 which includes a bolt-receiving groove (not shown) of conventional construction in which the head of bolts 68 are disposed. Each bolt 68 is tightened in place by a nut 70 when the clamp is in a position proximate to the mounting position of the stator 20. In addition, each clamp includes a clamp jaw 72 having a lower portion which is threadedly adjustable within the clamp and for mounting the stator 20. For that purpose, each jaw includes a stator support surface 74. As the result of the several clamps 18 a stator ranging in size from about 6 inches up to about 40 inches in diameter may be mounted on the device 10 for introducing and packing powdered resin 36 in place in the core slots.

For that purpose the vibrator 22 is attached by a plurality of bolts 76 to the undersurface of the support members 44. Good results were had using a vibrator 22 of the type having a reciprocating piston within a cylinder from which compressed air is exhausted alternately through air outlets 78 and 80 and in which air is applied through an air inlet 82. The speed at which the piston reciprocates vertically within the cylinder is dependent upon the air pressure involved. For example, at 10 pounds per square inch of air pressure, the piston reciprocates at a frequency of about 540 cycles per minute while at 100 pounds per square inch of air pressure, the piston reciprocates at about lllO cycles per minute. The vibration is transmitted to the support members 44 and the clamps to the stator 20. Other mechanisms for vibrating the table 10, may be employed in place of vi brator 22. Thus a vertically reciprocating solenoid can be substituted therefor. The direction of the vibration should be parallel to the axis of the stator or rotor slots. In one test the table 10 was vibrated with a rocking mechanism and far less satisfactory results were obtained than with vibration in the direction parallel to the stator axis. The frequency may vary from that given above, namely 540 to l l 10 cycles per minute, at which excellent results were obtained to as little as 100 cycles per minute to as much as 100 cycles per second.

As shown in FIG. 2, the schematic layout of the air system for operating the connectors or inflated cushions 50 as well as the vibrator 22, includes conduits 54 leading to the connectors 50 through a feed line through a source of air supply which may preferably be in the range of from about 90 to 150 psi. The air supply 82 for the vibrator leads to the same air supply. Each air supply is provided with suitable individual valve control means in a manner known in the art. Many stators were treated in the apparatus of the present invention, and tests and inspection of the cores after filling and even curing showed excellent insulation with the coils being well bonded.

During vibration, a supply of powdered resin 36 is placed on the top side of the stator 20 with the slots 84 extending vertically, and the resin particles drop downwardly through the several core slots 84 in which coil windings 86 have been previously mounted. To prevent the powdered resin 36 from dropping through the central armature or rotor opening in the stator 20 an inflatable bladder 88 having an air inlet 90 is placed in the center of the stator and inflated so that it presses against the core walls. In addition, a suitable wall 92 comprising, for example, metal foil is wrapped around the outer surface of the end turns 94 of the coil windings 86 to prevent the powdered resin 36 from spilling over the outer periphery of the stator 20.

As a result, during the vertical vibration of the table 16, the particles of powdered resin 36 move down wardly into the interstices and openings between the vertical portions of the coil windings 86 as well as adjacent to the walls forming the core slots 84 until the entire void space is filled with powder. During the preliminary part of the shaking operation a substantial portion of the particles of powdered resin 36 drop through the stator and are collected in the hopper 30. Subsequently, as the particles gradually fill in the spaces, wedge against each other and are compacted in place, they gradually build up a barrier against continued free movement of the resin through the stator slot. It is often desirable after the slots appear to be filled from the one end, the stator 20 may be turned over and powdered resin 36 may be vibrated through from the opposite end of the windings until the entire free volume of all of the slots 84 is filled.

Thereafter, the assembly of the stator 20 with its windings 86 surrounded with a compact filling of the powdered resin 36 within the slots 84 is removed from the device, placed in an oven and heated to a suitable temperature where the particles of resin 36 become fused and subsequently cured in place. In some cases the windings may be energized with electrical current to a temperature high enough to fuse the applied powdered resin.

Rotors or armatures may be similarly treated, except that an outer shield or inflatable tube can be placed around the outer periphery to enable resin powder to flow only into the slot.

Accordingly, the device of the present invention provides a device for mounting a stator or rotor and filling the core slots therein with a suitable powdered insulating material under vibration. The insulating material is preferably a powder comprising a heat hardenable resin. Exceptionally good results were had with a blend of an epoxy resin, and amine curing agent, and a silicon filler. A composition comprising 90 parts by weight of a potentially reactive epoxy resin, with 5% by weight of dicyandiamide, and 10 parts of silica of a fineness averaging 1 microns, was milled on hot rolls to form a uniform molten dispersion, without reaching a thermoset condition, cooled and powdered to a particle size wherein substantially all of the resin passed through a mesh sieve, and over 90% was retained on a mesh sieve. Procedures for making such compositions are set forth in US. Pat. No. 3,039,987.

Numerous other powdered resinous compositions may be employed. The compositions may comprise all resin with little or no fillers, or may include up to or more of finely divided fillers such as iron oxide, alumina, titanium dioxide, and finely divided mica, or mix tures of two or more. While epoxy resins have given good results, other hardenable resins may be substituted in whole or in part therefore. Other catalysts such as acid anhydrides may be employed. The powdered resinous material is preferably fusible at a temperature of from about 150F to 350F.

The resin composition can be ground to a fine powder which is screened to remove excessively coarse particles. A screened resin composition powder that passes through a 60 mesh screen (designated a 60 mesh pow der) will contain particles of various sizes, all passing through the 60 mesh sieve, includes some that will pass through a 200 mesh sieve, while a high proportion will be retained on this 200 mesh sieve. Good results have been obtained with 40 mesh, 60 mesh and 100 mesh powders. Powders of 150 mesh and 200 mesh can also be used.

The foregoing procedure and apparatus may be applied for insulating coils in stators of electrical equipment of varying sizes, ranging from about 6 inches to 6 feet in diameter an .svice being energized with upwardly of 3000 vol' The invention has been applied to both stators and re :rs of many sizes and shapes with excellent results.

it is understood that the above specification and drawings are merely exemplary and not in limitation of the invention.

What is claimed is:

ll. A method of packing a heathardenable resin in the form of a non-fluidized powder into the slots and spaces of stators of various sizes comprising:

1. positioning a stator with its slots in a substantially vertical position;

2. pouring said resin into the top of said slots and spaces;

3. vertically vibrating said stator until said resin has substantially filled said slots and spaces to the extent that said slots and spaces are substantially fillable from the top;

4. halting said vibration;

5. turning said stator upside-down;

6. repeating steps (2), (3) and (4); and

7. heating said stator to fuse and cure said resin.

2. A method according to claim 1 wherein the frequency of said vibration is 200 to 6000 cycles per min-

Claims (15)

1. A METHOD OF PACKING A HEATHARDENABLE RESIN IN THE FORM OF A NON-FLUIDIZED INTO THE SLOTS AND SPACES OF STATORS OF VARIOUS SIZES COMPRISING:

1. POSITIONING A STATOR WITH ITS SLOTS IN A SUBSTANTIALLY VERTICAL POSITION,

2. POURING SAID RESIN INTO THE TOP OF SAID SLOTS AND SPACES,

2. pouring said resin into the top of said slots and spaces;

2. A method according to claim 1 wherein the frequency of said vibration is 200 to 6000 cycles per minute.

3. vertically vibrating said stator until said resin has substantially filled said slots and spaces to the extent that said slots and spaces are substantially fillable from the top;

3. VERTICALLY VIBRATING SAID STATOR UNTIL SAID RESIN HAS SUBSTANTIALLY FILLED SAID SLOTS AND SPACES TO THE EXTENT THAT SAID SLOTS AND SPACES ARE SUBSTANTIALLY FILLABLE FROM THE TOP,

4. HALTING SAID VIBRATION,

4. halting said vibration;

5. turning said stator upside-down;

5. TURNING SAID STATOR UPSIDE-DOWN,

6. REPEATING STEPS (2), (3) AND (4), AND

6. repeating steps (2), (3) and (4); and

7. heating said stator to fuse and cure said resin.

7. HEATING SAID STATOR TO FUSE AND CRUDE SAID RESIN.

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